Question

Consider the trinomial x^2 + 3x − 40. as a first step to factoring it, find the factors of −40 such that the sum of those factors is 3. (enter your answers as a comma-separated list.)

Answer 1

What are factors of -40?
(-20)(2)
(-10)(4)   (sum of these factors is 6, which is not what we wanted)
(-5)(8) = -40 and the sum of the factors (-5) and (8) is 3.

{-5, 8} is the list of factors of -40 that add up to 3.