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

The two numbers are 10

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