Notice that 6 is a factor of all three coefficients and thus can be factored out:
6x^2 -42x-54 => 6(x^2 - 7x - 9). x^2 - 7x - 9 does not factor so easily. Remembering that obtaining roots of a quadratic makes it easy to write out the corresponding factors, let's apply the quadratic formula to x^2 - 7x - 9:
a=1, b = -7, c = -9. Then the discriminant is b^2 - 4ac, or (-7)^2 - 4(1)(-9), or 85.
Thus, the roots are:
7 plus or minus √85 7 plus or minus 9.220
x = -------------------------------- = ------------------------------------
2 2
Let's call these roots "a" and "b." Then the factors of the quadratic x^2 - 7x - 9 are (x-a) and (x-b), or, in this case, (x-8.11) and (x+1.11).
The original quadratic has three factors: 6, (x-8.11) and (x+1.11).
