How to use it
- For x²+bx, take half of b and square it.
- Add and subtract that square.
- Group the perfect-square trinomial.
See it in action
x²+6x+2 = (x+3)²−7.
How to verify it
Expand (x+3)²−7 = x²+6x+2.
Complete the Square
Completing the square rewrites a quadratic expression in vertex form and clarifies its geometry.