I do not see any binomials, but here is how to factor "5x^2+20x+15" so you can get the right binomials:
5x^2 + 20x + 15
= 5(x^2 + 4x + 3)
= 5(x^2 + x + 3x + 3)
= 5[(x^2 + x) + (3x + 3)]
= 5[x(x + 1) + 3(x + 1)]
= 5[(x + 1) (3x + 3)]
= 5(x + 1) (3x + 3)
