Question

sqrt(54)/(sqrt(sqrt(15)+3)*sqrt(sqrt(15)-3))

Answer 1

$frac{sqrt{54}}{sqrt{(sqrt{15}+3)*(sqrt{15}-3)}}=frac{3sqrt{6}}{sqrt{(sqrt{15})^2-3^2}}=frac{3sqrt{6}}{sqrt{15-9}}=frac{3sqrt{6}}{sqrt{6}}=3$