Factor the polynomial:3x^3-x^2-15x+5

(x^2-5) (3x-1)

Here's how I got this answer:

I found the GCF for each part of the polynomial.

3x^3 and - 15x both contain 3x, and - x^2 and 5 share - 1.

I then can divide the polynomial by 3x-1, and I get x^2-5

(Okay, that's not what I really did, but I can solve these on sight and don't remember the proper way to do it.)