Question 9 • Mathematics I
Complete the square: f(x) = -x² - 2x + 15 = -(x + 1)² + 16. Since (x + 1)² is always nonnegative, the function’s greatest value is 16, which it reaches at x = -1, so the range is y ≤ 16. The quadratic is defined for every real x, so its domain is all real numbers. Choice C gives both.
AI-written and checked against the verified answer.