Example

Completing the Square for x2−26xx^2 - 26x

To complete the square for the binomial x2−26xx^2 - 26x, we determine the constant needed to transform it into a perfect square trinomial. First, identify the coefficient of the linear term, which is −26-26. Next, compute the square of half of this coefficient: (12⋅(−26))2=(−13)2=169\left(\frac{1}{2} \cdot (-26)\right)^2 = (-13)^2 = 169. Adding this constant to the original expression yields the perfect square trinomial x2−26x+169x^2 - 26x + 169. Finally, this trinomial can be factored and written as the square of a binomial: (x−13)2(x - 13)^2. This demonstrates the standard procedure when the linear coefficient is a negative even integer, where the constant added is positive and the resulting binomial square uses subtraction.

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Updated 2026-05-15

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