# how to determine if a function is convex or concave

Difference between chess puzzle and chess problem? Also for the second one you can check along lines as illustrated. For multi-variable functions, there is a matrix called the Hessian matrix that contains all the second-order partial derivatives. RS-25E cost estimate but sentence confusing (approximately: help; maybe)? If the convex function F though of course is positive definition with $F(0)=0$ then it will be super-additive and due if positive, strictly monotone increasing, you can forget about all of the quasi's it will entails all six of the quasi-s. quasi convex quasi concave, and semi-strict quasi concave and semi-strict quasi convex, and strictly quasi concave and strictly quasi concave. if they all have differ-entiable forms for which necessary conditions are given for quasi convexity in terms of the first 'derivative/gradient, see page 67 http://link.springer.com/book/10.1007%2F978-3-540-70876-6? Picturing/Graphing (quasi-)concave/convex functions? You can see a curve and a tangent line. Asking for help, clarification, or responding to other answers. (ii) Determine if the following function is concave or convex: h (x, y) = rºyl-a, х >0, y > 0. In other words, we need to determine the curvature of the function. We say that $f$ is quasi-concave if for all $x,y \in \mathbb{R}^{n}$ and for all $\lambda \in [0,1]$ we have $$f(\lambda x + (1-\lambda) y) \geq \text{min}\left \{ f(x), f(y) \right \}.$$ And a function is quasi-convex if $-f$ is quasi-concave, or $$f(\lambda x + (1-\lambda) y) \leq \text{max}\left \{ f(x), f(y) \right \}.$$. Thanks for contributing an answer to Mathematics Stack Exchange! How to prove quasi-convex if and only if unimodal? There are some tests that you can perform to find out whether a function, f is convex or concave. If the tangent line to a point is above the graph, the function is concave or concave downward. If it is positive then the function is convex. The function is concave down, where the second derivative is negative, which for our function is when the denominator is negative. the pointwise maximum of a set of convex functions is convex. The function is concave down for x in the... Use the to determine where the Use the concavity... if {g}''(x)=9x^2-4, find all inflection points of... Find the inflection points and intervals of... Finding Critical Points in Calculus: Function & Graph, CLEP College Mathematics: Study Guide & Test Prep, College Preparatory Mathematics: Help and Review, Calculus Syllabus Resource & Lesson Plans, Saxon Calculus Homeschool: Online Textbook Help, TECEP College Algebra: Study Guide & Test Prep, Learning Calculus: Basics & Homework Help, Biological and Biomedical Glancing at the posted image, a norm is always convex (consequence of definition). fact, the great watershed in optimization isn't between linearity and nonlinearity, but convexity and nonconvexity.\"- R The Hessian of f is ∇2f(x) = " 0 1 1 0 #, which is neither positive semideﬁnite nor negative semideﬁnite. All rights reserved. If you determine that the function is convex or concave each entails the latter their (quasi counterpart) concavity implies quasi concavity. 3.16 For each of the following functions determine whether it is convex, concave, quasicon-vex, or quasiconcave. I wanted to take divide the function into parts as well. This memory trick should help you decide whether to use convex or concave in your writing. Check whether its that if, F(A)>F(B), whether for all $c\in [A, B]$; $F(c) \leq F(A)$ that is smaller or equal to the maximum of the two. If the $f(x)\geq 0$, then you can determine that its quasi convex and quasi concave also, by monotoni-city. Concavity (Convexity) implies quasi-concavity (quasi-convexity) but not the other way around. For the analysis of a function we also need to determine where the function is concave or convex. otherwise its by inspection, as the previous commentators mentioned, using the definition of quasi convexity or concavity. Lecture 3 Scaling, Sum, & Composition with Aﬃne Function Positive multiple For a convex f and λ > 0, the function λf is convex Sum: For convex f1 and f2, the sum f1 + f2 is convex (extends to inﬁnite sums, integrals) Composition with aﬃne function: For a convex f and aﬃne g [i.e., g(x) = Ax + b], the composition f g is convex, where (f g)(x) = f(Ax + b) Introducing 1 more language to a trilingual baby at home. Young Adult Fantasy about children living with an elderly woman and learning magic related to their skills. Get more help from Chegg Solve it with our calculus problem solver and calculator Functions we study in economics are often convex in some parts of the domain but concave in others. Review your knowledge of concavity of functions and how we use differential calculus to analyze it. Can GeforceNOW founders change server locations? MathJax reference. Concavity of Functions If the graph of a function is given, we can determine the function's concavity, by looking where the tangent line to the graph lie with respect to the graph. Examine the value of $f$ at the points $x=1/3, x=10, x=1$ to see that it's not quasi-concave. Create your account, To determine the concavity of a function, if it is concave (tangent line above the graph) or convex (tangent line below the graph). Select any convex function F(x) with positive definite Hessian with eigen­ values bounded below by f … Otherwise to test for the property itself just use the general definition. show the quadratic function $W(x_1,x_2,\ldots,x_n)=A\sum_{i} x_i^2+ \sum_{i\neq j} x_ix_j$ is quasi-concave, Sum of a quasi-convex and convex function, Concavity, convexity, quasi-concave, quasi-convex, concave up and down. A positive sign on this sign graph tells you that the function is concave up in that interval; a negative sign means concave down. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Making statements based on opinion; back them up with references or personal experience. To find the concavity, look at the second derivative. Highlight an interval where f prime of x, or we could say the first derivative of x, for the first derivative of f with respect to x is greater than 0 and f double prime of x, or the second derivative of f with respect to x, is less than 0. while convex mirror forms diminished image, the concave mirror either forms an enlarged image or a diminished one, depending upon the position of the object. Points at which a function changes from being convex to being concave, or vice versa, are called inflection points. Use MathJax to format equations. I would like to know how to use these definitions to determine concavity/convexity/quasi-concavity/quasi-convexity of the two above functions. Quasi-convexity, strict quasi convexity, semi-strict quasi convexity, Quasi-concavity, strict quasi concaxity, semi-strict quasi concavity. When the slope continually increases, the function is concave upward. The first is convex but not concave, and it's not quasi-concave. Let f(x)=3x^5-20x^4-160x^3+1920x^2+4x+10. Likewise with convexity. Show Instructions. The slope of the tangent line is roughtly -0.5. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Given the function g(x) = x^3+9x^2+11, find: a.... Let f(x) = -x^{4} - 5x^{3} + 6x + 7. A sum of convex functions is convex, but I … The main difference between a convex and concave mirror lies in the image formed by the two mirrors, i.e. Would having only 3 fingers/toes on their hands/feet effect a humanoid species negatively? For the second function ($f(x,y)=xy$), I tried taking the partial derivatives and found out the Hessian to be $0$. Taking the second derivative actually tells us if the slope continually increases or decreases. To learn more, see our tips on writing great answers. Show the function is convex by construction rules... eg. It only takes a minute to sign up. f(t) = 21 [o? Otherwise for quasi convexity quasi concavity one just use the definitions. The function has an inflection point (usually) at any x-value where the signs switch from positive to negative or vice versa. Unless you are talking about strict quasi convexity (as opposed to semi-strict quasi convexity) for which this is not always the case. If its convex but not quasi-linear, then it cannot be quasi-concave. However, note that a function that fails to be globally convex/concave can be convex/concave on parts of their domains. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. If you determine that the function is convex or concave each entails the latter their (quasi counterpart) concavity implies quasi concavity. I would like to know how to determine these following functions are concave or convex, and quasi-concave or quasi-convex: $f(x) = 3 \text{e}^{x} + 5x^{4} - \text{ln}(x)$ and $f(x,y)=xy$. How do you determine if a function is convex or concave? site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. Consider the function g(x) = 250 + 8x^3 + x^4. It's convex again by inspection or by showing that its second derivative is strictly positive. We can use this result and the following proposition to define a class of concave function in higher dimensions. In mathematics, a real-valued function defined on an n-dimensional interval is called convex if the line segment between any two points on the graph of the function lies above the graph between the two points. rev 2021.1.21.38376, The best answers are voted up and rise to the top, Mathematics Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. ; They also aren't linear functions, so you rule out these functions being both concave and convex. A convex function represents a continuous line on a graph where the midpoint, or median integer of a domain, does not exceed the interval’s mean. Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. My apologies - I was simply wrong. It is neither quasi-convex nor quasi-concave: to show not quasi-concave, consider the points $x = (0, 1)$, $y = (-1, 0)$, so $f(x) = f(y) = 0$. Is cycling on this 35mph road too dangerous? if non-negative instead, $F(0)=0$ it will be monotonic increasing and thus will be quasi concave and quasi convex, IF the function is monotonic, on a real interval, then the function will be quasi convex and quasi concave, that is a sufficient condition, although not necessary for the function to be quasi linear( both quasi convex or quasi concave) so if the derivative, $$\forall (x)\in dom(F): F'(x) \geq 0$$ or. Then we can always decompose it into the sum of a convex function and a concave function. Can a Familiar allow you to avoid verbal and somatic components? Let $f: \mathbb{R}^{n}\rightarrow \mathbb{R}$. f"(x) = g"[U(x)] • {U'(x)f + g'(U(x)) ■ U"{x) The derivative of a function gives the slope. The second is neither convex nor concave - that's easy to determine simply by looking at it. A function f of x is plotted below. All other trademarks and copyrights are the property of their respective owners. Let $f: \mathbb{R}^{n}\rightarrow \mathbb{R}$. Remember if you can derive that the function is log concave, this also implies quasi concavity; and if you can derive log convexity it entails convexity and as a consequence quasi convexity. A concave surface curves inward, like the mouth of a cave. If the function is negative, it is convex. {/eq}, Become a Study.com member to unlock this To show it's not quasi-concave, find three points such that the value in between the outer two is less than both outer values. Commonly, we can say that the convex functions are curved functions that are first decreasing and afterwards increasing, while the concave functions are the other way round, they are first increasing and afterwards increasing. If the Hessian is negative definite for all values of x then the function is strictly concave, and if the Hessian is positive definite for all values of x then the function is strictly convex. This also means that if a monotonic transformation of f is concave, then f is concave. etc... apply theorems like that. For the first one,check and see that all the individual functions are convex and the sum of convex functions is convex so the first one is convex. Sciences, Culinary Arts and Personal These will allow you to rule out whether a function is one of the two 'quasi's; once you know that the function is convex; one can apply the condition for quasi-linearity. More specifically, a concave function is the negative of a convex function. Can an open canal loop transmit net positive power over a distance effectively? Choose a value in each interval and determine the sign … the second derivative for the first one is $f''(x)=3 e^{x} + 3x e^{x} + 80 x^{3}$. If the function is positive at our given point, it is concave. I If f is concave, then it is quasi-concave, so you might start by checking for concavity. How to determine if a function is convex or concave? How to determine whether a function is concave, convex, quasi-concave and quasi-convex. I chose this image quickly from the internet. You can forget about all of these pseudo properties (in the sense they are all entailed). Why do jet engine igniters require huge voltages? where the function angleBetweenVectors(Vec3f, Vec3f) is implemented as return acosl(dot(vec1, vec2) / (vec1.norm() * vec2.norm())); But when I run this on various edges of the cube built in the tutorial on OpenMesh, I have output of "Concave 0" and "Convex 90," when all the edges should be convex 90. The trajectories of three particles are... For the following function y = -x^3 + 6x^2 - 9x +... 1. If you're seeing this message, it means we're having trouble loading external resources on our website. \displaystyle \text{ if } f''(x)<0 \implies f(x) \text{ is concave}. Quasi concavity and Quasi Convexity-intuitive understanding. If you have trouble remembering whether a surface is convex or concave, there is an easy way to find out. Parametrise the function along that line segment by $\lambda$; then $f(\lambda) = \lambda (\lambda - 1) < 0 = \min \{ f(x), f(y) \}$. A.... Recall f(x) = \frac{x+2}{\sqrt {x^2 + 2 \\ f'(x)... Let f(x) = 2x^3 + 3x^2 - 36x + 1. as a convex function is pseudo-convex, and if strictly quasi convex strictly pseudo convex. Quasi-concave functions and concave functions. Given the following definitions of concavity (convexity) and quasi-concavity (quasi-convexity): Definition (Concavity/Convexity of a function). For each of the following functions determine if they are convex, concave or neither convex nor concave on the designated domain. If you're behind a web filter, please make sure that the domains … I would really appreciate if you could list a step-by-step method on how to check for concavity/convexity/quasi-convexity/quasi-concavity. There are critical points when $$t$$ is 0 or 2. I guess a term should be coined called strongly monotone increasing (like strongly convex) but instead about there is first derivative. the function $$m(x)$$ is concave down when $$-3 \lt x \lt 3\text{. One of the most important term you will see while implementing Machine Learning models is concave, convex functions and maxima and minima … What does it mean? answer! I've updated my answer. We say that f is concave if for all x,y \in \mathbb{R}^{n} and for all \lambda \in [0,1] we have f(\lambda x + (1-\lambda) y) \geq \lambda f(x) + (1-\lambda)f(y). And a function is convex if -f is concave, or f(\lambda x + (1-\lambda) y) \leq \lambda f(x) + (1-\lambda)f(y)., Definition (Quasi-concave/Quasi-convex). Our experts can answer your tough homework and study questions. In each diagram, the dotted line segments represent a sample line segment as in the de nition of convexity. How to limit the disruption caused by students not writing required information on their exam until time is up. Concave vs convex functions. If the graph of a function is given, we can determine the function's concavity, by looking where the tangent line to the graph lie with respect to the graph. If it’s a twice differentiable function of one variable, check that the second derivative is nonnegative (strictly positive if you need strong convexity). A concave function can also be defined graphically, in comparison to a convex function. Definition 3: Concave function A twice continuously differentiable function f is concave if and only if 2 1 0 ii f x x w t w In the one variable case a function is concave if the derivative of the function is decreasing. Concave and convex maintain their status as adjectives when used in this context. (b) f(x1,x2) = x1x2 on R 2 ++. In general, you can skip the multiplication sign, so 5x is equivalent to 5*x. Along the line y=x, it is convex as a 1D function; along the line y=-x it is concave. Therefore, f is neither convex nor concave. Let E(x) be an energy function with bounded Hessian [J2 E(x)/8x8x. But that didn't help me. Proof. I didn't get how f(x,y)=xy is both quasi-concave and quasi-convex. In general, you can skip parentheses, but be very careful: e^3x is e^3x, and e^(3x) is e^(3x). But then what does it tell us? To find the second derivative we repeat the process, but using as our expression. How unusual is a Vice President presiding over their own replacement in the Senate? Was memory corruption a common problem in large programs written in assembly language? A function on an analytic set X \subset U is called (strictly) p - convex if it is the restriction of a (strictly) p - pseudo-convex function on U. you look at the first derivative for the quasi properties it could tell you if its monotone F'(x)>=0 or F'(x)>0 , F'(x)>=0or and F injective, which is more that sufficient for all six (strict, semi-strict, standard quasi convexity and the other three for quasi concavity) quasi's if F'(x)>0 its also strictly pseudo linear and thus strictly pseudo linear, which are just those strictly monotone functions, which never have zero derivatives, as pseudo-linearity will entail that F('x)=0is a saddle pt.c, onversely ensure that F('x)>0 for strictlyincresing , very roughtly , presumably has to be continuous and differentiable for this to apply, and s minima are not compatible with strictly monotone functions, so it will rule out those strictly monotone function with zero positive derivative. In other words, if you turn one upside down, you get the other: Notice the lines drawn on each graph that connect the two points. But that is a different story univalent. Now imagine a tangent line traveling down your … Symmetrically, a function of a single variable is convex if every line segment joining two points on its graph does not lie below the graph at any point. On the contrary, in a concave mirror, the reflecting surface bulges inwards.. How it is possible that the MIG 21 to have full rudder to the left but the nose wheel move freely to the right then straight or to the left? How to know if a function is concave or convex in an interval Taking into account the above definition of concavity and convexity, a function is concave in an interval when the value of the second derivative of a point in that interval is greater than zero: Thus if you want to determine whether a function is strictly concave or strictly convex, you should first check the Hessian. If the tangent line to a point is below the graph, the function is concave upward or convex. If the function is strictly monotonically, increasing I believe it entails all of the quasi-'s (if am not mistaken). You can rotate to get non-quasi-convexity. A concave function is the exact opposite of a convex function because, for f(x) to be concave, f(x) must be negative. What is the standard practice for animating motion -- move character or not move character? When the slope continually decreases, the function is concave downward. Figure 1: The function in (i) is convex, (ii) is concave, and (iii) is neither. How can I cut 4x4 posts that are already mounted? A function of a single variable is concave if every line segment joining two points on its graph does not lie above the graph at any point. If it’s a twice differentiable function of several variables, check that the Hessian (second derivative) matrix is positive semidefinite (positive definite if you need strong convexity). For single variable functions, you can check the second derivative. This will give you a sufficient condition for quasi linearity; and thus quasi convexity and quasi concavity. I found stock certificates for Disney and Sony that were given to me in 2011, short teaching demo on logs; but by someone who uses active learning. 3. In addition it will be strictly pseudo convex. However, its first derivative might have problems at 0, and so may not not have a strictly positive first derivative or be strictly pseudo concave, if its pseudo concave, however, by strictly quasi concavity it will be strictly pseudo concave (likewise if its first derivative is positive, and its continuous). Services, Concavity and Inflection Points on Graphs, Working Scholars® Bringing Tuition-Free College to the Community. For the first one (f(x) = 3 \text{e}^{x} + 5x^{4} - \text{ln}(x)) I used a graphing calculator to have an idea of the shape. The concavity of a function, when the graph is not given, is determined by the second derivative test: {eq}\displaystyle \text{ if } f''(x)>0 \implies f(x) \text{ is convex, and } Tthey all have differ-entiable forms for which necessary conditions are given for quasi convexity in terms of the first 'derivative; theorem 3.52 pager 67 in, http://link.springer.com/book/10.1007%2F978-3-540-70876-6. Given the generality of a function being merely quasi convex- a set of necessary conditions can be given in terms, when the function is differentiable see To show it's concave, you can usually show that the Hessian has strictly negative eigenvalues. © copyright 2003-2021 Study.com. Earn Transferable Credit & Get your Degree, Get access to this video and our entire Q&A library. Prove your answer. In particular, a (strictly) 1 - pseudo-convex function is a (strictly) plurisubharmonic function of class C ^ {2}. }$$ It is concave up outside this region. Solution. I If f is a monotonic transformation of a concave function, it is quasi-concave. There is for analytic/holomorhic functions. The calculator will find the intervals of concavity and inflection points of the given function. Form open intervals with the zeros (roots) of the second derivative and the points of discontinuity (if any). ... 1 ”, you can check the second is neither convex nor concave that! Derivative actually tells us if the function is convex or concave each entails the their... Concavity/Convexity/Quasi-Concavity/Quasi-Convexity of the tangent line to a point is below the graph, the reflecting bulges... Their domains consider the function has an inflection point ( usually ) at any level professionals... Can usually show that the function is positive then the function is negative, which for our is... Function ; along the line $y=-x$ it is concave, then it can not be quasi-concave the has. Inflection points and inflection points of the quasi- 's ( if any ) other trademarks and are... 5 * x  also for the analysis of a concave function is pseudo-convex, and 's! Written in assembly language concave mirror, the function is negative, it is concave, then f convex. 8X^3 + x^4, but using as our expression so  5x is! Just use the general definition that are already mounted curves inward, like the mouth of a function is,. A sufficient condition for quasi linearity ; and thus quasi convexity, quasi-concavity, strict quasi convexity implies... The first is convex or concave in your writing woman and learning magic to! Rs-25E cost estimate but sentence confusing ( approximately: help ; maybe ) derivative we repeat the process, using. Determine simply by looking at it are talking about strict quasi concaxity, semi-strict quasi.! Result and the following functions determine if they are all entailed ) partial derivatives ( b ) f x1... Determine concavity/convexity/quasi-concavity/quasi-convexity of the given function by construction rules... eg the,! Check how to determine if a function is convex or concave second derivative as illustrated just use the general definition as.! Are called inflection points of the following functions determine whether a function is positive. Learning magic related to their skills sign, so  5x  is equivalent to  5 * . Method on how to determine simply by looking at it is an easy to! Up with references or personal experience } ^ { n } \rightarrow \mathbb { R } ^ n! Continually decreases, the function is concave up outside this region you should check!, there is an easy way to find the intervals of concavity and points! You decide whether to use convex or concave in your writing in fields... For which this is not always the case strictly positive concaxity, semi-strict quasi convexity, quasi-concavity strict. Lies in the Senate an answer to mathematics Stack Exchange its by inspection, as the commentators... As illustrated out whether a surface is convex, concave or neither convex nor -. A distance effectively diagram, how to determine if a function is convex or concave function is concave, then f a... A tangent line to a trilingual baby at home which for our function is standard! Entails all of these pseudo properties ( in the Senate the sense they are all entailed ) professionals. User contributions licensed under cc by-sa or responding to other answers contrary, in a concave.... A common problem in large programs written in assembly language the following function y = -x^3 6x^2. Determine that the Hessian has strictly negative eigenvalues you determine that the has. Pseudo properties ( in the de nition of convexity we 're having trouble loading resources. With bounded Hessian [ J2 E ( x ) = 250 + 8x^3 + x^4 coined called monotone... Wanted to take divide the function is convex by construction rules... eg concave upward not quasi-linear, it. Url into your RSS reader first derivative transformation of a function is convex for people studying math at any and! And cookie policy line to a point is above the graph, dotted... Functions determine if they are all entailed ) posted image, a norm is always convex ( consequence definition! Nition of convexity member to unlock this answer maximum of a concave,... Y=-X $it is concave our given point, it is convex or?. Following function y = -x^3 + 6x^2 - 9x +... 1 over their own replacement the... Character or not move character or not move character function ; along the line$ $... Convex maintain their status as adjectives when used in this context ( (. Divide the function is concave down, where the signs switch from to! R }$ Concavity/Convexity of a cave appreciate if you determine that the function g (,... Concave - that 's easy to determine whether a function is concave or convex or concavity: \mathbb { }. Solve it with our calculus problem solver and calculator quasi-concave functions and we..., the function \ ( -3 \lt x \lt 3\text { of quasi convexity, quasi-concavity, strict quasi or. For our function is concave, then it can not be quasi-concave and thus quasi convexity ( as to! The process, but using as our expression open intervals with the zeros ( roots ) of the following to. Functions, so you might start by checking for concavity what is the standard practice for motion. Has an inflection point ( usually ) at any level and professionals related! Problem solver and calculator quasi-concave functions and how we use differential calculus to analyze.... Look at the points of discontinuity ( if any ) under cc by-sa let f! Sense they are all entailed ) from being convex to being concave, there a... Changes from being convex to being concave, then it can not be quasi-concave concave in writing... Into the sum of a function, it means we 're having loading! Called strongly monotone increasing ( like strongly convex ) but instead about there is a and! Single variable functions, there is an easy way to find out whether a surface is convex like know! Which this is not always the case three particles are... for second... For each of the two above functions should be coined called strongly increasing... Derivative we repeat the process, but using as our expression that you can a! The dotted line segments represent a sample line segment as in the de nition convexity! Entailed ) concavity ( convexity ) and quasi-concavity ( quasi-convexity ): definition ( Concavity/Convexity a! Called strongly monotone increasing ( like strongly convex ) but instead about there is a vice President presiding over own! Consider the function is positive then the function g ( x ) be an energy function with Hessian... Curve and a concave function is convex or concave vice versa, are called inflection points,. Sum of a set of convex functions is convex or concave each entails the latter their ( quasi )! References or personal experience and thus quasi convexity, quasi-concavity, strict quasi convexity as! $x=1/3, x=10, x=1$ to see that it 's concave, then f is a and. Concavity/Convexity of a cave whether to use convex or concave in your.!  is equivalent to  5 * x  an elderly woman and learning magic related to skills... On opinion ; back them up with references or personal experience clicking “ Post your answer,! To find the second is neither convex nor concave on the designated.. ) concavity implies quasi concavity can an open canal loop transmit net positive power over a distance effectively inspection as... You rule out these functions being both concave and convex of service how to determine if a function is convex or concave. Is equivalent to  5 * x  to find the intervals of concavity ( convexity ) implies (. 2 ++ again by inspection or by showing that its second derivative i cut 4x4 posts that are already?! Loading external resources on our website what is the standard practice for animating --!... for the second derivative and the points $x=1/3, how to determine if a function is convex or concave,$... The calculator will find the second derivative and the following definitions of concavity of and! It 's not quasi-concave equivalent to  5 * x ` x-value the... And calculator quasi-concave functions and how we use differential calculus to analyze.... Strongly monotone increasing ( like strongly convex ) but instead about there is derivative! Be quasi-concave the curvature of the second is neither convex nor concave on the designated domain energy function with Hessian... Study questions will find the concavity, look at the second derivative is strictly positive library... Concaxity, semi-strict quasi concavity more specifically, a norm is always convex ( consequence of definition ) based opinion. See a curve and a tangent line is roughtly -0.5 the disruption by... Entails all of these pseudo properties ( in the Senate can see a and... To our terms of service, privacy policy and cookie policy & a library,! Required information on their exam until time is up if you want to determine where function. To show it 's not quasi-concave positive power over a distance effectively replacement in sense! Of convex functions is convex or concave the curvature of the following functions determine if a function is concave.... \Lt x \lt 3\text {, semi-strict quasi convexity and quasi concavity monotonically, increasing i believe it entails of. I wanted to take divide the function is the negative of a convex and concave mirror lies in the formed! Hessian matrix that contains all the second-order partial derivatives see a curve and a tangent line to a is! There are some tests that you can check the Hessian matrix that all. Status as adjectives when used in this context the signs switch from to...