Factor the expression 10x2 + 20x - 80

10x^2  + 20x  - 80   take out the  greatest common factor, 10

10  (x^2  + 2x  - 8)

To factor the polynomial, we need two numbers that add to 2  and multiply to  -8.....

4  and -2    seem to be  just right....so we have

10 ( x + 4) ( x - 2)

I'm a bit confused, would I expand the two polynomials then multiply the answer all by 10?