Question: how to factor quadratic expressions of the form ax2+bx+c?
Answer: Write out all the pairs of numbers that, when multiplied, produce a.
Write out all the pairs of numbers that, when multiplied, produce c.
Pick one of the a pairs -- (a1, a2) -- and one of the c pairs -- (c1, c2).
If c > 0: Compute a1c1 + a2c2.