I need to find and classify stationary points of:
z = x^2 + 4xy + 4y - 9x + 1
so far I got:
dz/dx = 2x + 4y - 9 and dz/dy = 4x + 4
not sure as to how to go on as Im rubbish at these lol
Thanks
Your two equations are (we have already told you what they are using your partial derivatives of z):
dz/dx = 2x + 4y - 9=0
and:
dz/dy = 4x + 4=0.
The second of these tells you that for any critical point x=-1, so using the first you find 4y-11=0 or y=11/4.
So now you have the critical point, now you need to determine what type it is.
CB