Answer
$s^{2}+12st^{2}+36t^{4}$
Work Step by Step
$(s+6t^{2})^{2}$
Using the rule of
$(a+b)^{2}$ = $a^{2}$+2ab+$b^{2}$
In this case, the a= s and b= $6t^{2}$ as substituting these gives us the original polynomial
$a^{2}$+2ab+$b^{2}$
$s^{2}$+2(s)($6t^{2}$)+$(6t^{2})^{2}$
Thus,
$s^{2}+12st^{2}+36t^{4}$
