Two things you need to know.
a square root that is squared becomes the number under the root sign
the general formula is a^2 + 2ab + b^2
sqrt(5)^2 + 2*sqrt(5)*sqrt(3) + sqrt(3)^2
5 + 2sqrt(15) + 3
8 + 2sqrt(15) <<<<=====
Stop!
Don't go any further. That is your answer.
