How do I find the local minimum of z=sqrt(x^2+y^2)(adsbygoogle = window.adsbygoogle || []).push({});

I know its simple, but I'm stuck on it. I've tried using the second derivative but it just goes exponential. Then I tried using the second derivative test but did'nt succeed. And kindly could someone solve it step by step as it makes it much more understandable.

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# Local minimum of z=(x^2+y^2)^(1/2)

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