Explanation Given: The function is given as: z = x 3 − 8 y 2 + 6 x y + 4 Formula used: f x x ( x , y ) = ∂ f x ∂ x f y y ( x , y ) = ∂ f y ∂ y f x y ( x , y ) = ∂ f x ∂ y M = f x x ( a , b ) ⋅ f y y ( a , b ) − [ f x y ( a , b ) ] 2 Calculation: Since the function is a polynomial function, so partial derivatives always exist. Find all the points ( a , b ) such that f x ( a , b ) = 0 and f y ( a , b ) = 0 . Assume z = f ( x , y ) , To find f x ( x , y ) differentiate f ( x , y ) = x 3 − 8 y 2 + 6 x y + 4 with respect to x and take y as constant, use the Power Rule for f ( x , y ) = x n + y n + x m y m , Calculate the value of f x . f x ( x , y ) = n x n − 1 + 0 + m x m − 1 y m = n x n − 1 + m x m − 1 y m Similarly, f y ( x , y ) = 0 + n y n − 1 + x m m y m − 1 = n y n − 1 + x m m y m − 1 Now, f x = 3 x 3 − 1 − 0 + 6 x 1 − 1 y + 0 = 3 x 2 + 6 y And, f y = 0 − 8 ( 2 ) y 2 − 1 + 6 x y 1 − 1 + 0 = − 16 y + 6 x . Set each of these two partial derivatives equal to 0. 3 x 2 + 6 y = 0 and − 16 y + 6 x = 0 . These two equations form a system of linear equations that can be rewritten as: x 2 + 2 y = 0 − 8 y + 3 x = 0 To solve this system by elimination, multiply the first equation by 4 and then add the equations: 4 x 2 + 8 y = 0 − 8 y + 3 x = 0 After addition, 4 x 2 + 3 x = 0 x ( 4 x + 3 ) = 0 x = 0 , − 3 4 Substitute x = 0 in the first equation of the system, x 2 + 2 y = 0 ( 0 ) 2 + 2 y = 0 y = 0 Substitute x = − 3 4 in the first equation of the system, x 2 + 2 y = 0 ( − 3 4 ) 2 + 2 y = 0 9 16 + 2 y = 0 y = − 9 32 Thus, ( 0 , 0 ) and ( − 3 4 , − 9 32 ) are the points where the given function z = x 3 − 8 y 2 + 6 x y + 4 have any local extrema. Suppose f ( x , y ) is a function such that f x x , f y y , and f x y all exist. Assume ( a , b ) be a critical point for which f x ( a , b ) = 0 and f y ( a , b ) = 0 . Let M be the number defined by: M = f x x ( a , b ) ⋅ f y y ( a , b ) − [ f x y ( a , b ) ] 2 1. There exists a local maximum at the point ( a , b ) if the value of M is M > 0 and f x x ( a , b ) < 0 . 2. There exists a local minimum at the point ( a , b ) if M > 0 and f x x ( a , b ) > 0 . 3. The saddle point is at the point ( a , b ) if M < 0 . 4. There is no information available if the value of M is M = 0 . To find f x x ( x , y ) differentiate f x with respect to x and take y as constant, use the Power Rule for f x ( x , y ) = n x n − 1 + m x m − 1 y m . Calculate the value of f x x

Mathematics with Applications and Mylab Math with Pearson EText -- Title-Specific Access Card Package

12th Edition

ISBN: 9780134862668

Author: Lial, Margaret L.

Publisher: Pearson Education Canada

See similar textbooks

Concept explainers

Minimization

In mathematics, traditional optimization problems are typically expressed in terms of minimization. When we talk about minimizing or maximizing a function, we refer to the maximum and minimum possible values of that function. This can be expressed in ter…

Maxima and Minima

The extreme points of a function are the maximum and the minimum points of the function. A maximum is attained when the function takes the maximum value and a minimum is attained when the function takes the minimum value.

Derivatives

A derivative means a change. Geometrically it can be represented as a line with some steepness. Imagine climbing a mountain which is very steep and 500 meters high. Is it easier to climb? Definitely not! Suppose walking on the road for 500 meters. Which …

Concavity

In calculus, concavity is a descriptor of mathematics that tells about the shape of the graph. It is the parameter that helps to estimate the maximum and minimum value of any of the functions and the concave nature using the graphical method. We use the …

Videos

Question

Chapter 14, Problem 42RE

To determine

To calculate: All the points where the provided function z=x3−8y2+6xy+4 has any local extrema and saddle points.

Expert Solution & Answer

Want to see the full answer?

Check out a sample textbook solution

See solution

Chapter 14, Problem 41RE

Chapter 14, Problem 43RE

Students have asked these similar questions

7. [10 marks] Let G = (V,E) be a 3-connected graph. We prove that for every x, y, z Є V, there is a cycle in G on which x, y, and z all lie. (a) First prove that there are two internally disjoint xy-paths Po and P₁. (b) If z is on either Po or P₁, then combining Po and P₁ produces a cycle on which x, y, and z all lie. So assume that z is not on Po and not on P₁. Now prove that there are three paths Qo, Q1, and Q2 such that: ⚫each Qi starts at z; • each Qi ends at a vertex w; that is on Po or on P₁, where wo, w₁, and w₂ are distinct; the paths Qo, Q1, Q2 are disjoint from each other (except at the start vertex 2) and are disjoint from the paths Po and P₁ (except at the end vertices wo, W1, and w₂). (c) Use paths Po, P₁, Qo, Q1, and Q2 to prove that there is a cycle on which x, y, and z all lie. (To do this, notice that two of the w; must be on the same Pj.)

6. [10 marks] Let T be a tree with n ≥ 2 vertices and leaves. Let BL(T) denote the block graph of T. (a) How many vertices does BL(T) have? (b) How many edges does BL(T) have? Prove that your answers are correct.

4. [10 marks] Find both a matching of maximum size and a vertex cover of minimum size in the following bipartite graph. Prove that your answer is correct. ย ພ

Chapter 14 Solutions

Mathematics with Applications and Mylab Math with Pearson EText -- Title-Specific Access Card Package

Ch. 14.1 - Prob. 1CP Ch. 14.1 - Prob. 2CP Ch. 14.1 - Prob. 3CP Ch. 14.1 - Prob. 4CP Ch. 14.1 - Prob. 5CP Ch. 14.1 - Prob. 1E Ch. 14.1 - Prob. 2E Ch. 14.1 - Prob. 3E Ch. 14.1 - Prob. 4E Ch. 14.1 - Prob. 5E

Ch. 14.1 - Prob. 6E Ch. 14.1 - Prob. 7E Ch. 14.1 - Prob. 8E Ch. 14.1 - Prob. 9E Ch. 14.1 - Prob. 10E Ch. 14.1 - Prob. 11E Ch. 14.1 - Prob. 12E Ch. 14.1 - Prob. 13E Ch. 14.1 - Prob. 14E Ch. 14.1 - Prob. 15E Ch. 14.1 - Prob. 16E Ch. 14.1 - Prob. 17E Ch. 14.1 - Prob. 18E Ch. 14.1 - Prob. 19E Ch. 14.1 - Prob. 20E Ch. 14.1 - Prob. 21E Ch. 14.1 - Prob. 22E Ch. 14.1 - Prob. 23E Ch. 14.1 - Prob. 24E Ch. 14.1 - Prob. 25E Ch. 14.1 - Prob. 26E Ch. 14.1 - Prob. 27E Ch. 14.1 - Prob. 28E Ch. 14.1 - Prob. 29E Ch. 14.1 - Prob. 30E Ch. 14.1 - Prob. 33E Ch. 14.1 - Prob. 34E Ch. 14.1 - Prob. 31E Ch. 14.1 - Prob. 32E Ch. 14.1 - Prob. 38E Ch. 14.1 - Prob. 35E Ch. 14.1 - Prob. 36E Ch. 14.1 - Prob. 37E Ch. 14.1 - Work these exercises. Checkout Lines According to...Ch. 14.1 - Prob. 40E Ch. 14.1 - Prob. 41E Ch. 14.1 - Prob. 42E Ch. 14.1 - Prob. 43E Ch. 14.1 - Prob. 44E Ch. 14.1 - Prob. 45E Ch. 14.1 - Prob. 46E Ch. 14.1 - Prob. 47E Ch. 14.1 - Prob. 48E Ch. 14.2 - Prob. 1CP Ch. 14.2 - Prob. 2CP Ch. 14.2 - Prob. 3CP Ch. 14.2 - Prob. 4CP Ch. 14.2 - Prob. 5CP Ch. 14.2 - Prob. 6CP Ch. 14.2 - Prob. 7CP Ch. 14.2 - Prob. 8CP Ch. 14.2 - Prob. 9CP Ch. 14.2 - Prob. 1E Ch. 14.2 - For each of the given functions, find the...Ch. 14.2 - Prob. 3E Ch. 14.2 - Prob. 4E Ch. 14.2 - Prob. 5E Ch. 14.2 - Prob. 6E Ch. 14.2 - Prob. 7E Ch. 14.2 - Prob. 8E Ch. 14.2 - Prob. 9E Ch. 14.2 - Prob. 10E Ch. 14.2 - Prob. 11E Ch. 14.2 - Prob. 12E Ch. 14.2 - Prob. 13E Ch. 14.2 - Prob. 14E Ch. 14.2 - Prob. 15E Ch. 14.2 - Prob. 16E Ch. 14.2 - Prob. 17E Ch. 14.2 - Prob. 18E Ch. 14.2 - Prob. 19E Ch. 14.2 - Prob. 20E Ch. 14.2 - Prob. 21E Ch. 14.2 - Prob. 22E Ch. 14.2 - Prob. 23E Ch. 14.2 - Prob. 24E Ch. 14.2 - Prob. 25E Ch. 14.2 - Prob. 26E Ch. 14.2 - Prob. 27E Ch. 14.2 - Prob. 28E Ch. 14.2 - Prob. 29E Ch. 14.2 - Prob. 30E Ch. 14.2 - Prob. 31E Ch. 14.2 - Prob. 32E Ch. 14.2 - Prob. 33E Ch. 14.2 - Prob. 34E Ch. 14.2 - Prob. 35E Ch. 14.2 - Prob. 36E Ch. 14.2 - Prob. 37E Ch. 14.2 - Find fx,fy,fz, and fyz for the given functions. In...Ch. 14.2 - Prob. 39E Ch. 14.2 - Suppose z=f(x,y) describes the cost to build a...Ch. 14.2 - Prob. 41E Ch. 14.2 - 42. Business The revenue from the sale of x units...Ch. 14.2 - Prob. 62E Ch. 14.2 - Prob. 44E Ch. 14.2 - Prob. 45E Ch. 14.2 - Prob. 43E Ch. 14.2 - Prob. 42E Ch. 14.2 - Prob. 59E Ch. 14.2 - Prob. 50E Ch. 14.2 - Prob. 51E Ch. 14.2 - Work the following applied problems. (See Example...Ch. 14.2 - Prob. 53E Ch. 14.2 - Work the following marginal productivity problems....Ch. 14.2 - Prob. 55E Ch. 14.2 - Prob. 56E Ch. 14.2 - Prob. 58E Ch. 14.2 - Work the following applied problems. (See Example...Ch. 14.2 - Prob. 48E Ch. 14.2 - Prob. 49E Ch. 14.2 - Prob. 61E Ch. 14.2 - Prob. 57E Ch. 14.2 - Prob. 60E Ch. 14.3 - Prob. 1CP Ch. 14.3 - Prob. 2CP Ch. 14.3 - Prob. 3CP Ch. 14.3 - Prob. 4CP Ch. 14.3 - Prob. 1E Ch. 14.3 - Prob. 2E Ch. 14.3 - Prob. 3E Ch. 14.3 - Prob. 4E Ch. 14.3 - Prob. 5E Ch. 14.3 - Prob. 6E Ch. 14.3 - Prob. 7E Ch. 14.3 - Prob. 8E Ch. 14.3 - Prob. 9E Ch. 14.3 - Prob. 10E Ch. 14.3 - Prob. 11E Ch. 14.3 - Prob. 12E Ch. 14.3 - Prob. 14E Ch. 14.3 - Prob. 13E Ch. 14.3 - Prob. 15E Ch. 14.3 - Prob. 16E Ch. 14.3 - Prob. 17E Ch. 14.3 - Prob. 18E Ch. 14.3 - Prob. 19E Ch. 14.3 - Prob. 20E Ch. 14.3 - Prob. 21E Ch. 14.3 - Prob. 22E Ch. 14.3 - Prob. 23E Ch. 14.3 - Prob. 24E Ch. 14.3 - Prob. 25E Ch. 14.3 - Prob. 26E Ch. 14.3 - Prob. 27E Ch. 14.3 - Prob. 28E Ch. 14.3 - Prob. 29E Ch. 14.3 - Prob. 30E Ch. 14.3 - Prob. 31E Ch. 14.3 - Prob. 32E Ch. 14.3 - Prob. 33E Ch. 14.3 - Prob. 34E Ch. 14.3 - Prob. 35E Ch. 14.3 - Prob. 36E Ch. 14.3 - Prob. 37E Ch. 14.3 - Prob. 38E Ch. 14.3 - Prob. 39E Ch. 14.3 - Prob. 40E Ch. 14.3 - Prob. 41E Ch. 14.3 - Prob. 42E Ch. 14.3 - Prob. 43E Ch. 14.3 - Prob. 44E Ch. 14.4 - Prob. 1CP Ch. 14.4 - Prob. 2CP Ch. 14.4 - Prob. 1E Ch. 14.4 - Prob. 2E Ch. 14.4 - Prob. 3E Ch. 14.4 - Prob. 4E Ch. 14.4 - Prob. 5E Ch. 14.4 - Prob. 6E Ch. 14.4 - Prob. 7E Ch. 14.4 - Prob. 8E Ch. 14.4 - Prob. 9E Ch. 14.4 - Prob. 10E Ch. 14.4 - Prob. 11E Ch. 14.4 - Prob. 12E Ch. 14.4 - Prob. 13E Ch. 14.4 - Prob. 14E Ch. 14.4 - Prob. 15E Ch. 14.4 - Prob. 16E Ch. 14.4 - Prob. 17E Ch. 14.4 - 18. Explain the difference between the two methods...Ch. 14.4 - Prob. 19E Ch. 14.4 - Prob. 20E Ch. 14.4 - Prob. 21E Ch. 14.4 - Prob. 22E Ch. 14.4 - Prob. 23E Ch. 14.4 - Prob. 24E Ch. 14.4 - Prob. 25E Ch. 14.4 - Prob. 26E Ch. 14.4 - Prob. 27E Ch. 14.4 - Prob. 28E Ch. 14.4 - Prob. 29E Ch. 14.4 - Prob. 30E Ch. 14.4 - Prob. 31E Ch. 14.4 - Prob. 32E Ch. 14.4 - Prob. 33E Ch. 14.4 - Prob. 34E Ch. 14.4 - Prob. 35E Ch. 14.4 - Prob. 36E Ch. 14 - Prob. 1RE Ch. 14 - Prob. 2RE Ch. 14 - Prob. 3RE Ch. 14 - Prob. 4RE Ch. 14 - Prob. 5RE Ch. 14 - Prob. 6RE Ch. 14 - Prob. 7RE Ch. 14 - Prob. 8RE Ch. 14 - Prob. 9RE Ch. 14 - Prob. 10RE Ch. 14 - Prob. 11RE Ch. 14 - Prob. 12RE Ch. 14 - Prob. 13RE Ch. 14 - Prob. 14RE Ch. 14 - Prob. 15RE Ch. 14 - Prob. 16RE Ch. 14 - Prob. 17RE Ch. 14 - Prob. 18RE Ch. 14 - Prob. 19RE Ch. 14 - Prob. 20RE Ch. 14 - Prob. 21RE Ch. 14 - Prob. 22RE Ch. 14 - Prob. 23RE Ch. 14 - Prob. 24RE Ch. 14 - Prob. 25RE Ch. 14 - Prob. 26RE Ch. 14 - Prob. 27RE Ch. 14 - Prob. 28RE Ch. 14 - Prob. 29RE Ch. 14 - Prob. 30RE Ch. 14 - Prob. 31RE Ch. 14 - Prob. 32RE Ch. 14 - Prob. 33RE Ch. 14 - Prob. 34RE Ch. 14 - Prob. 35RE Ch. 14 - Prob. 36RE Ch. 14 - Prob. 37RE Ch. 14 - Prob. 38RE Ch. 14 - Prob. 39RE Ch. 14 - Prob. 40RE Ch. 14 - Prob. 41RE Ch. 14 - Prob. 42RE Ch. 14 - Prob. 43RE Ch. 14 - Prob. 44RE Ch. 14 - Prob. 45RE Ch. 14 - Prob. 46RE Ch. 14 - Prob. 47RE Ch. 14 - Prob. 48RE Ch. 14 - Prob. 49RE Ch. 14 - Prob. 50RE Ch. 14 - 51. Find positive numbers x and y whose sum is 80...Ch. 14 - Prob. 52RE Ch. 14 - Prob. 53RE Ch. 14 - Prob. 54RE Ch. 14 - Prob. 1CE Ch. 14 - Prob. 2CE

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, subject and related others by exploring similar questions and additional content below.

All the points where the provided function z = x 3 − 8 y 2 + 6 x y + 4 has any local extrema and saddle points.

Concept explainers

Videos

To calculate: All the points where the provided function z=x3−8y2+6xy+4 has any local extrema and saddle points.

Want to see the full answer?

Chapter 14 Solutions