An expression such as x2 + 8x is an "incomplete" square. But if you add 16 to x2 + 8x, we will get x? + 8x + 16 which is a perfect square trinomial and equivalent to (x + 4)2 in factored form. When we add 16 to x2 + 8x, we are completing the square. Factored Form Look for a pattern in the following table. Incomplete Square Completed Square x² + 4x x² + 4x + 4 y² + 6y y² + 6y + 9 b28b b2-8b + 16 m2 - 10m m2- 10m + 25 (x + 2)2 ( + 3)2 (b-4)2 (m - 5)2​