Question

Using complete sentences, explain how to completely factor 2x2 - 8x - 42.

Answer 1

First factor out 2. You get:
2(x^2 - 4x - 21)

Then, find factors of 21 such that their difference is 4. Seems like 7 and 3 will do.

So, you have:
2(x-7)(x+3)