Question

How do you solve `x^2 + 2x = 3` by completing the square?

Answer 1

`x = 1` or `x = -3`

Explanation:

In `x^2 + 2x` a third term is missing to be able to write the square of a binomial.
Find it by dividing the coefficient of `x` by 2, square it and add to both sides.

`x^2 + 2x + color(red)1 = 3 + color(red)1`

`(x + 1)^2 = 4`

`x + 1 = +-sqrt4 = +-2`

`x = +2 - 1` or `x = -2-1`

`x = 1` or `x = -3`