In general if there is no critical number, the extrema can be found at the extremities of the interval you consider.

You can see that -2/x² is always negative, whatever x is. Hence the function isstrictlydecreasing.

So if you consider the interval [1,2], the absolute maximum will be at 1 and the absolute minimum will be at 2.

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Now you should get back to the definition of a critical point. It's a point where the derivative is 0ora point where the derivative is undefined.

So x=0 is a critical point.

But yes, it doesn't give any extrema.

An absolute minimum can be found by looking at the limit of the function as x goes to infinity. The function will always be "above" this value.