Which of the following is the standard form of the polynomial function y = x(x + 5)(x − 3)?

First multiply the two binomials: (x + 5)(x − 3) = x² + 2x − 15. Then multiply by the remaining x to get y = x³ + 2x² − 15x. This matches choice D, y = x³ + 2x² − 15x.

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