I am studying for the GRE and reviewing math I haven't seen in years. I've got the answer and have solved similar problems, but am having trouble understanding a specific step in the factoring. I realize asking you folks is a lot like using an AT4 to shoot an ant, but I would appreciate the assistance if you could help.

The problem is Solve 3x^2+11x−4=0

The solution to the factoring process shows the following 3 steps:
Step 1: =3x^2+12x−x−4
Step 2: =3x(x+4)−1(x+4)
Step 3: =(3x−1)(x+4)

I can figure out everything through step 2 and after step 3, but I can't figure out how they factored step 2 into step 3.

Thanks for the help.
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