Definition :

A critical number of a function $\"\"$ is a number $\"\"$ in the domain of $\"\"$ such that either $\"\"$

or $\"\"$ does not exist. $\"\"$

The function is $\"\"$ .

Since there should not be any negative number in the square root, the domain of the function is $\"\"$ .

Differentiate $\"\"$ on each side with respect to $\"\"$ .

$\"\"$

Equate $\"\"$ to zero :

$\"\"$

$\"\"$ is undefined $\"\"$ .

The critical points are $\"\"$ and $\"\"$ .

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