Answer 1

It sounds like you have a problem that is asking you to factorize the quadratic
(x + α)(x + β) = 0
Where you need to figure out α and β.
Completing the square is the method I usually use to find them, though there are a few, for instance when required I have the quadratic formula memorized.
https://en.wikipedia.org/wiki/Quadratic_formula
https://www.youtube.com/watch?v=YtN9_tCaRQc
https://www.youtube.com/watch?v=prx_Bf2hakw
these links may help