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So f(x,y) = xe^{-x}(y^{2}- 4y)

Find all stationary points and classify them i got

for f_{x}(x,y) s.p (1,4),(1,0)

for f_{y}(x,y) s.p (0,2)

I thought that you don't need double differentials at this stage and if it is a s.p it must satisfy

for f_{x}(x0,y0) = 0

for f_{y}(x0,y0) = 0

which means s.p must hold for both partial derivatives?

I know the s.ps are wrong so if someone could advise that would be great.

Josh

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# Two-Variable Optimisation Confusion

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