2 x - 6*x - 7
x^2 - 6*x - 7
2 -7 + x - 6*x
-7 + x^2 - 6*x
(x + 1)*(x - 7)
-7.0 + x^2 - 6.0*x
-7 + x*(-6 + x)
(1 + x)*(-7 + x)