Question

How do you complete the square for #x^2 + 9?

Answer 1

Since `(x+a)^2 = x^2+2ax+a^2`

If `x^2` and `(+9)` are two terms of an expression of an expansion of the form `(x+a)^2`
then
`a = +-3`

and there are 2 possible ways of "completing the square"

`x^2+9 = (x+3)^2 -6x`
or
`x^2+9 = (x-3)^2 +6x`