How to determine the solutions of equation x^2+2x-8=0, completing the square?

We have the equation x^2 + 2x - 8 = 0 to solve by completion of
square.

We know that (a + b)^2 = a^2 + b^2 +
2ab

x^2 + 2x - 8 = 0

=> x^2 + 2x
+ 1 - 8 -1 = 0

=> (x + 1)^2 - 9 =
0

=> (x + 1)^2 = 9

Now we
get

x + 1 = sqrt 9 and x + 1 = -sqrt
9

x = -1 + sqrt 9 and x = -1 - sqrt 9

x
= -1 + 3 and x = -1 - 3

x = 2 and x =
-4

The solution of the equation is x = 2 and x =
-4