2 x + 8*x + 15
x^2 + 8*x + 15
2 15 + x + 8*x
15 + x^2 + 8*x
(x + 5)*(x + 3)
15.0 + x^2 + 8.0*x
15 + x*(8 + x)
(3 + x)*(5 + x)