Find the critical points of the following functions.Use the Second

sagnuhh

sagnuhh

Answered question

2021-10-13

Find the critical points of the following functions.Use the Second Derivative Test to determine (if possible) whether each critical point corresponds to a local maximum, a local minimum,or a saddle point. If the Second Derivative Test is inconclusive,determine the behavior of the function at the critical points.
f(x, y)=(4x1)2+(2y+4)2+1

Answer & Explanation

Fatema Sutton

Fatema Sutton

Skilled2021-10-14Added 88 answers

Step 1
Given function is f(x)=(4x1)2+(2y+4)2+1=16x2+4y28x+16y+18
We find critical points:
fx=fx=32x8
fy=fdy=8y+16
Setting these equal to zero,
32x8=0, x=14
8y+16=0, y=2
So, the critical point is {(14, 2})
Now we find the second derivatives,
f×=32
fyy=8
fxy=0
So, D=f××fyy(fxy)2
For {(14, 2})
D=32×80=256>0
Since D>0 and f×{(14, 2})=32>0, so the obtained critical point is a local minimum.

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