Hello,

Find and such that and

These are the critical points.

I hope you've done bits of algebra including matrices...

The Hessian matrix is defined at a point as :

Work with eigenvalues

If the eigenvalues are all positive, then this point is a maximum.

If they are all negative, then this point is a minimum.

If one is positive and one is negative, then this point is a saddle point.

Work with discriminant

If the discriminant is negative, then it's a saddle point.

If the discriminant is positive and , then it's a maximum.

If the discriminant is positive and , then it's a minimum.

If you don't know how to proceed, google for Hessian matrix.