What substitution should be used to rewrite 16(x3 + 1)2 – 22(x3 + 1) – 3 = 0 as a quadratic equation?

The repeated expression is (x³ + 1), appearing both squared and to the first power. Set u = (x³ + 1); then the equation becomes 16u² − 22u − 3 = 0, a quadratic in u. The correct choice is B, u = (x³ + 1).

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