How is x squared plus 4x -8 equals zero

X^2 + 4x - 8 = 0

Move constant to right side.

x^2 + 4x = 8

Let's complete the square to find x.

(4/2)^2 = 4

We add 4 to both sides.

x^2 + 4x + 4 = 8 + 4

Factor left side.

(x + 2)(x + 2) = 12

(x + 2)^2 = 12

Take square root on both sides.

sqrt{(x + 2)^2} = sqrt{12}

x + 2 = 2•sqrt{3}

x + 2 = -2•sqrt{3}

Two answers:

x = - 2 + 2•sqrt{3}

And

x = -2 - 2•sqrt{3}