What side lengths should be used to model a rectangle with an area of x2 + 3x – 10 square units?

Factor the area expression by finding two numbers whose product is −10 and whose sum is 3. Those numbers are −2 and 5, so x² + 3x − 10 = (x − 2)(x + 5). The rectangle’s side lengths should therefore be x − 2 and x + 5, which is choice B.

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