2 z + 5*z - 6
z^2 + 5*z - 6
(x + 6)*(x - 1)
2 -6 + z + 5*z
-6 + z^2 + 5*z
-6.0 + z^2 + 5.0*z
(-1 + z)*(6 + z)
-6 + z*(5 + z)