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Example

Completing the Square for x2+14xx^2 + 14x

Complete the square for the expression x2+14xx^2 + 14x to form a perfect square trinomial, then express the result as a binomial square.

Step 1 — Identify bb. The coefficient of xx is 1414, so b=14b = 14.

Step 2 — Find (12b)2\left(\frac{1}{2}b\right)^2. Compute half of 1414: 1214=7\frac{1}{2} \cdot 14 = 7. Square the result: 72=497^2 = 49.

Step 3 — Add 4949 to the expression.

x2+14x+49x^2 + 14x + 49

Rewrite as a binomial square. The completed trinomial factors as:

x2+14x+49=(x+7)2x^2 + 14x + 49 = (x + 7)^2

This example applies the completing-the-square procedure when the linear coefficient is a positive even integer. Taking half of 1414 yields 77, and squaring 77 produces the constant 4949 that transforms the two-term expression into the perfect square trinomial (x+7)2(x + 7)^2.

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Updated 2026-04-21

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