Question

How do you complete the square to solve `x^2+2x-10=14`?

Answer 1

If you first add `11` to both sides you get:

`x^2+2x+1 = 25`

Now

`x^2+2x+1 = (x+1)(x+1) = (x+1)^2`

and `25 = 5^2`

So we have

`(x+1)^2 = 5^2`

Hence

`x+1 = +-sqrt(5^2) = +-5`

Subtracting 1 from both sides we get:

`x = -1 +-5`

That is `x = 4` or `x=-6`