(x – 7)(x + 3) =

Multiply each term in the first parentheses by each term in the second: x·x = x², x·3 = 3x, −7·x = −7x, and −7·3 = −21. Combining the middle terms gives x² + 3x − 7x − 21 = x² − 4x − 21, which is choice B.

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