What is the solution set of –(x + 4)(x – 5) ≤ 0?

Multiply both sides of –(x + 4)(x – 5) ≤ 0 by –1 and reverse the inequality, giving (x + 4)(x – 5) ≥ 0. The product is nonnegative when both factors have the same sign, which happens for x ≤ –4 or x ≥ 5; include the endpoints because equality is allowed. The solution is (–∞, –4] U [5, ∞), choice D.

AI-written and checked against the verified answer.