Definition :

A critical number of a function $\"\"$ is a number $\"\"$ in the domain of $\"\"$ such that either $\"\"$ or $\"\"$ does not exist.

$\"\"$

The function is $\"\"$ .

There should not be any negative number in the square root.

$\"\"$

Domain of the function $\"\"$ is $\"\"$ .

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

$\"\"$

Equate $\"\"$ to zero :

$\"\"$

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

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