x^2 + x - 20 = 0

Question

solve by using the zero product property

Answer 1

Problem: x^2 + x - 20 = 0
solve by using the zero product property

x^2 + x - 20 = 0
(x + 5)(x - 4) = 0

Either one of the factors, or both, must equal zero.

(x + 5) = 0
x = -5

(x - 4) = 0
x = 4

Check.

x^2 + x - 20 = 0
(-5)^2 + (-5) - 20 = 0
25 - 5 - 20 = 0
0 = 0

x^2 + x - 20 = 0
4^2 + 4 - 20 = 0
16 + 4 - 20 = 0
0 = 0

Answer: x = 4 and x = -5