Please help me find the min or max...?

Question

F(x,y) = -x^2 - 2y^2 + 6x -4y

a.) find max or min

please help me solve this problem, i would really thank you from the bottom of my heart.

Answer 1

Fx(x,y) = -2x + 6

Fy(x,y) = -4y - 4

F(3,-1) = critical point, more specifically a maximum (since in this case both second derivatives are negative)

Fxx = -2

Fyy = -4

Answer 2

i think u should differentiate it with respect to X, & another time with respect to Y. then make x=0 one time & also y. i think so