Find he local maximum and minimum value and saddle points of the function? Find he local maximum and minimum value and saddle points of the function: $$f(x,y)=x^2-xy+y^2-9x+6y+10$$
The answer is a min of $(-4,1), f(-4,1)=73$
I got a min of $(12/5,-21/5)$
my
$$
f_x=2x-y-9\\
f_y=-x+2y+6
$$
set $f_x = 0 = f_y$ and we get $x=(9+y)/2$ so $y=-21/5$ and $x=12/5$
I found out that this was a minimum by the 2nd derivative test. There are no max or saddle points.

You're both wrong (or maybe you made a mistake in copying $f$): the minimum is at $(4,-1)$ where the value is $-11$.
