Answer:
At critical point in D
a

b

where

c
maximum value 11
minimum value 10
Explanation:
Given

At critical point

=>
![[f'(x,y)]_x = 20x =0](https://img.qammunity.org/2021/formulas/mathematics/college/dow11ey6tr7a60jz9m15gkntpsf659hf3j.png)
=>

Also
![[f'(x,y)]_y = 22y =0](https://img.qammunity.org/2021/formulas/mathematics/college/33w7b8xg62b2hiepiaoz5l5uvpdosoc8s9.png)
=>

Now considering along the boundary

=>

=>

Restricting
to this boundary


At boundary point D = 1
Which implies that
or
So the range of x is

Now along this this boundary the critical point is at

=>

=>

Now at maximum point



For the minimum point x = -1 or x =1



