We can either use the quadratic formula or completing the square.
I'll use the method if completing the square.
x^2 + 10x + 12 = 36
Move the constant over to the other side.
x^2 + 10x = 24
Add (b/2)^2 to both sides.
x^2 + 10x + (10/2)^2 = 24 + (10/2)^2
x^2 + 10x + 5^2 = 24 + 5^2
x^2 + 10x + 25 = 24 + 25
Factor the left side and add the terms on the right side
(x+5)(x+5) = 49
(x+5)^2 = 49
Find the square root of both sides.
x + 5 = +/- 7
Move 5 over to the other side by subtracting it.
x = -5 + -7 = -12
OR
x = -5 - (-7) = 2
So x = -12 or x = 2.
