Question

What 2 numbers multiply to equal 20 and add to make -9?

Answer 1

The two numbers are 10

Answer 2

first number: x

second number: y

Sum: x + y = -9 ⇒ y = -x - 9

Product: xy = 20 ⇒ x(-x - 9) = 20

-x² - 9x = 20

0 = x² + 9x + 20

0 = (x + 4)(x + 5)

0 = x + 4 or 0 = x + 5

x = -4 or x = -5

y = -x - 9 ⇒ y = -(-4) - 9 = -5 or y = -(-5) - 9 = -4

Answer: -4, -5