2 x + 3*x - 28
x^2 + 3*x - 28
2 -28 + x + 3*x
-28 + x^2 + 3*x
(x + 7)*(x - 4)
-28.0 + x^2 + 3.0*x
-28 + x*(3 + x)
(-4 + x)*(7 + x)