At what base is square root of 120 natural number

Question

I got this problem i need to solve: At what base b, where b>2 , (120)_b equals x², where x is in decimal number system? I need to find all bases b, and i need to see the process of finding answer, so i can do it myself.

Answer 1

$(120)_b = b^2+2b$

$b^2+2b$ can never be a perfect square as $b^2+2b+1$ is (except for $b=0$).