The function is $\"\"$ .

The tangent of a curve will be horizontal, if slope of the tangent line is zero.

Slope of the tangent line is derivative of the function.

$\"\"$

Equating $\"\"$ to zero.

$\"\"$ .

Roots of the quadratic equation $\"\"$ are $\"\"$ .

Compare $\"\"$ with $\"\"$ .

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

Substitute above values in the formula $\"\"$ .

$\"\"$

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

Graph of the function has horizontal tangent at $\"\"$ and $\"\"$ .

The function has horizontal tangent at $\"\"$ and $\"\"$ .