So we first find where fx(x,y) = 0 and fy(x,y) = 0, where fx and fy are the partial derivatives of z = f(x,y). Once we find those critical points, we use D = (fxx)(fyy) - (fxy)^2.(adsbygoogle = window.adsbygoogle || []).push({});

If D > 0 and fxx > 0, we have a local min at that point.

If D > 0 and fxx < 0, we have a local max at that point.

If D < 0, we have a saddle point.

If D = 0, no information can be found using the second derivative test.

My question is:

1. How do we deal with the D = 0 situation? How would we find if that point's a max or min?

2. What if fxx = 0?

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# Homework Help: Finding min and max

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