Example

Completing the Square for x2+6xx^2 + 6x

Complete the square for the expression x2+6xx^2 + 6x to form a perfect square trinomial, then express the result as a binomial square.

Step 1 — Identify bb. The coefficient of the linear term is 6, so b=6b = 6.

Step 2 — Find (12b)2\left(\frac{1}{2}b\right)^2. Take half of bb and square it: (126)2=32=9\left(\frac{1}{2} \cdot 6\right)^2 = 3^2 = 9

Step 3 — Add the constant to complete the square. Add 9 to the original expression: x2+6x+9x^2 + 6x + 9

Step 4 — Factor the trinomial. Rewrite the perfect square trinomial as a binomial square: x2+6x+9=(x+3)2x^2 + 6x + 9 = (x + 3)^2

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Updated 2026-07-01

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