The Second Partials Test states that if a function f(x,y) has continuous second partials and fx(x0,y0) = 0 and fy(x0,y0) = 0, then
1. H > 0 and fxx(x0,y0) > 0 implies (x0,y0) is a local minimum;
2. H > 0 and fxx(x0,y0) < 0 implies (x0,y0) is a local maximum;
3. H < 0 implies (x0,y0) is a saddle point;
4. H = 0 then the test is inconclusive.