$\"\"$

The formula for surface area of a cone is $\"\"$ .

Solve $\"\"$ for l.

Subtract $\"\"$ from each side.

$\"\"$

Divide each side by $\"\"$ .

$\"\"$

Cancel common terms.

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

Substitute the value of $\"\"$ in the formula $\"\"$ .

$\"\"$

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

The solutions $\"\"$ .