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Critical number :

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

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$\"\"$

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The function is $\"\"$ .

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

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

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$\"\"$

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Apply quotient rule of derivatives : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Equate $\"\"$ to zero :

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$\"\"$

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Find the solutions of the quadratic equation :

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$\"\"$

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$\"\"$ and $\"\"$

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$\"\"$ and $\"\"$ .

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

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Thus, the critical numbers are $\"\"$ and $\"\"$ .

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