First, get all the term to one side:
4x^2 + 36x + 120 = 0
Then, factor out the greatest common factor of the terms.
4(x^2 + 9x + 30) = 0
Next, this trinomial is not factorable, so you need to use the quadratic formula:
(-9 +- sqrt(81 -4(1)(30))) / 2(1)
Both solutions to this quadratic are imaginary
x = (-9 + isqrt(39)) / 2
x = (-9 - isqrt(39)) / 2
