X2 + X =12
I do not understand how to solve this problem
x^2 + x = 12
x^2 + x - 12 = 0
Find factors of 12, with a difference of 1. 4 and 3 will do.
(x + 4)(x - 3) cross multiplying will give us 4x - 3x = x
Either (x + 4) = 0 or (x - 3) = 0. Solve both.
x + 4 = 0
x = -4
x - 3 = 0
x = 3
You have two possible values for x: - 4 and 3. Try both
in the original equation.
x^2 + x = 12
(-4)^2 + (-4) = 12
16 - 4 = 12
12 = 12 checks
x^2 + x = 12
3^2 + 3 = 12
9 + 3 = 12
12 = 12 checks
Answer: x = -4, and x = -3