Suppose that
has continuous second partial derivatives in a neighbourhood of
and that
at![]()
Define
at
Form the discriminant
If
then
is a saddle point.

If
then
has a local minimum at![]()

If
and a local maximum at
if![]()

Suppose that
has continuous second partial derivatives in a neighbourhood of
and that
at![]()
Define
at
Form the discriminant
If
then
is a saddle point.

If
then
has a local minimum at![]()

If
and a local maximum at
if![]()
