SOLUTION: What two factors multiply to equaul 72 but add up to be negative 18?

Algebra ->  Expressions-with-variables -> SOLUTION: What two factors multiply to equaul 72 but add up to be negative 18?      Log On


   

Question 426986: What two factors multiply to equaul 72 but add up to be negative 18?
Answer by htmentor(1343) About Me  (Show Source):
You can put this solution on YOUR website!
x*y = 72
x + y = -18 -> y = -18 - x
Substitute in the 1st equation:
x*(-18 - x) = 72 -> -x^2 - 18x - 72 = 0 -> x^2 + 18x + 72 = 0
Quadratic formula gives:
x+=+%28-18+%2B-+sqrt%2818%5E2+-+4%2A%2872%29%29%29%2F2
Solving for x gives:
x = -6,-12
Therefore, y = -18 - -6 = -12 or y = -18 - -12 = -6.
So the two numbers are: -6,-12