Use substitution to write an equivalent quadratic equation.(3x + 2)2 + 7(3x + 2) – 8 = 0

Let u = 3x + 2, since that expression appears both squared and as a first-power term. Substituting gives u² + 7u − 8 = 0, which is choice B. Using u = (3x + 2)² would not correctly replace the first-power term.

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