12. Find the local maximum and minimum values and saddle point(s) of the function f(x, y) = -x4 + 4.xy – 2y² + 1. %3D

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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Please answer question 12 below!
11. Find an equation of the tangent plane to the surface Va+V+Vz=4 at the point P(4, 1,1).
12. Find the local maximum and minimum values and saddle point(s) of the function f(x, y) =
-x4 + 4xy – 2y² + 1.
%3D
13. Find the maximum value of the function f(x, y) = 6 – 4x² – y? subject to the constraint
4x +y = 5.
%3D
14. Find the maximum and minimum values of the function f(x,y) = xy on the ellipse given
by the equation x² +
=1.
4
%3D
Transcribed Image Text:11. Find an equation of the tangent plane to the surface Va+V+Vz=4 at the point P(4, 1,1). 12. Find the local maximum and minimum values and saddle point(s) of the function f(x, y) = -x4 + 4xy – 2y² + 1. %3D 13. Find the maximum value of the function f(x, y) = 6 – 4x² – y? subject to the constraint 4x +y = 5. %3D 14. Find the maximum and minimum values of the function f(x,y) = xy on the ellipse given by the equation x² + =1. 4 %3D
Expert Solution
Step 1

Given that, fx, y=-x4+4xy-2y2+1.

Differentiating f with respect to x and y,

fx=-4x3+4yfy=4x-4y

To find the critical points, consider, fx=0 and fy=0,

-4x3+4y=0  14x-4y=0  2

Adding the above equations,

-4x3+4x=04x-x2+1=0

Therefore, x=0 or x=1 or x=-1

Step 2

Substitute the values of x in equation (2),

y=0 or y=1 or y=-1

Therefore, the critical points are 0,0, 1,1 and -1,-1.

Differentiating fx with respect to x.

fxx=-12x2

Differentiating fy with respect to y.

fyy=-4

Differentiating fx with respect to y.

fxy=4

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