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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 the denominator is never zero, the domain of the function is all real numbers.

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$\"\"$ is differentiable on its domain.

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Therefore, solutions of $\"\"$ , $\"\"$ are the critical numbers.

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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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The critical numbers are $\"\"$ .

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The critical numbers are $\"\"$ .