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
