Absolute Minima and Maxima

[MAHAH8]

Could you please explain to me how to find absolute extrema in this problem:
F(x,y)=x^2+xy+y^2 on the sequare -2<=x, y=<2

Thanks in advance.

 

[tkhunny]

1) Have you considered the partial derivatives?

2) Derivatives don't know about edges where derivatives don't exist.