Which area model will form four parts x², 7x, −3x, and −21?

Correct answer: (x + 7)(x − 3)

Direct answer: Option A, (x + 7)(x − 3), is correct. In an area model, one side is divided into lengths x and 7, while the other side is divided into lengths x and −3. Multiplying every row length by every column length gives four signed rectangular parts: x·x = x², 7·x = 7x, x·(−3) = −3x, and 7·(−3) = −21. Their sum is x² + 7x − 3x − 21. Option B gives −7x and +3x instead, so its signs do not match. Option C makes both cross-products positive, giving +7x and +3x. Option D makes both cross-products negative, giving −7x and −21? More precisely, it gives −7x, −3x, and +21, so it also fails. Memory cue: the signs of the four parts come directly from multiplying the signs on the two sides.