$\"\"$

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The function is $\"\"$ on interval $\"\"$ .

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$\"\"$

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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Apply formula : $\"\"$ .

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Apply formula : $\"\"$ .

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$\"\"$

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$\"\"$ .

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The slope of the tangent is $\"\"$ .

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$\"\"$

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To find horizontal tangent by equating slope of the tangent is zero.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Apply zero product property.

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

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

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

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If $\"\"$ , then $\"\"$ on $\"\"$ .

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If $\"\"$ , then $\"\"$ on $\"\"$ .

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The solutions of $\"\"$ are $\"\"$ .

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Horizontal tangent at $\"\"$ .

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$\"\"$

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Find the points in the interval $\"\"$ where the function has a horizontal tangents.

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Horizontal tangents at $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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The point is $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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The point is $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The point is $\"\"$ .

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Horizontal tangent at the points $\"\"$ , $\"\"$ and $\"\"$ .

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$\"\"$

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Horizontal tangent at the points $\"\"$ , $\"\"$ and $\"\"$ .