What is the completely factored form of x3 + 4x2 – 9x – 36?

Group the terms: x³ + 4x² − 9x − 36 = x²(x + 4) − 9(x + 4) = (x² − 9)(x + 4). Then factor the difference of squares, x² − 9 = (x + 3)(x − 3), giving (x + 3)(x − 3)(x + 4), choice C.

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