At least on this one you have made an effort! The whole point of taking partial derivatives is that the critical points occur where the derivatives are 0!

Solve and 2y= 0.

Yes, with a and b the values you got by solving those equations.I know I'm supposed to use this rule:

d=fxxfyy-(fxy)^2

If d>0:

fxx(a,b)>0, then f(a, b) is a rel min

fxx(a,b)<0, then f(a,b) is a rel. max

If d<0, it's a saddle point.

Please help! Thank you