Question

How do you solve by completing the square for `x^2-8x+7`?

Answer 1

You have to take half the `x`-coefficient (=-4) and square it. At the same time you have to balance the 7 that is allready there.

Explanation:

`x^2-8x+16=(x-4)^2`

So we need to add `9` to both sides:
`x^2-8x+16=9->`
`(x-4)^2=9->`
So: `x-4=sqrt9=3->x=7`
Or: `x-4=-sqrt9=-3->x=1`