Question

Find the critical point of the given function and then determine whether it is a local maximum, local minimum, or saddle point.

Answer 1

critical point of the given function f(x,y) = x²+y²+2xy is from line y = -x is the critical point of the function f(x0,y0) = 0

and it local minimum.

Explanation:

Let the given function be;

f(x,y) = x²+y²+2xy

From above function, we can locate relative minima, maxima and the saddle point

f(x,y) = x²+y²+2xy = (x+y)²

df/dx = 2x+2y = 0 ---- (1)

df/dy =2y+2x = 0 ---- (2)

From eqn 1 and 2 above,

The arbitrary point (x0,y0) from line y = -x is the critical point of the function f(x0,y0) = 0

Then, from f(x,y) >= 0 for arbitrary (x,y) € R^n, the arbitrary point from the line x = -y is local minima of the function f.