Partial derivative of f(x, y) to y =-4-2y=0, y=-2.
The second derivative of f(x, y) to x =-2
The second derivative of f(x, y) to y =-2
The partial derivative of f(x, y) to x and then to y =0.
Because -2 *-2-0 2 = 4 > 0, (2, -2) is an extreme value.
F(x, y) to x Second order =-2
f(2,-2)=8