Question

How do you solve using the completing the square method `x^2+8x-9=0`?

Answer 1

Completing the square is designed to give you a perfect square trinomial on the left of an equation.

Explanation:

1. Get any constants on the right side.
   `x^2+8x=9`

2. Add `(b/2)^2=(8/2)^2` to both sides
   `x^2+8x+16=9+16`

3. Factor the left.
   `(x+4)^2=25`

4. Square root both sides.
   `(x+4)=+-5`

5. `x={5-4,-5-4} = {1,-9}`