Question

How do you complete the square to solve `x^2 + 6x = -8`?

Answer 1

Given `x^2+6x = -8`

If `x^2+6x` are the first two terms of a squared binomial of the form:
`color(white)("XXXX")` `(x+a)^2 = x^2+2ax+a^2`
then
`color(white)("XXXX")` `a=3`

`x^2 +6x +9 = -8 +9`

`(x+3)^2 = 1`

`x+3 = +-1`

`x= -2` or `x=-4`