Which of the binomials below is a factor of this trinomial? 5x2 + 20x + 15

Factor the following:

5 x^2 + 20 x + 15

Factor 5 out of 5 x^2 + 20 x + 15:

5 (x^2 + 4 x + 3)

The factors of 3 that sum to 4 are 3 and 1. So, x^2 + 4 x + 3 = (x + 3) (x + 1):

Answer: 5 (x + 3) (x + 1)