Which is the completely factored form of 3x2 – 12x – 15?

First factor out the greatest common factor, 3: 3x² − 12x − 15 = 3(x² − 4x − 5). The numbers −5 and 1 multiply to −5 and add to −4, so x² − 4x − 5 = (x − 5)(x + 1). Therefore, the completely factored form is 3(x + 1)(x − 5), choice A.

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