in the problem f(x,y)=x^2+y^2 and xy=1, I get 2 as a local extrema and it is a min(adsbygoogle = window.adsbygoogle || []).push({});

in the problem f(x1,x2...xn) = x1+x2..+xn (x1)^2+...(xn)^2=1 I get sqrt(n) and its a max. How do I know if these are max or min values? If I get more than two extrema, I just compare them and one's a max and the other's min. What if there's only one?

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# Lagrange multipliers: How do I know if its a max of min

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