ACT Math · Function notation and transformations
What is the range of f(x) = -(x-2)² + 9?
What is the range of ?
Answer and explanation
Answer: A: y ≤ 9
The function is a parabola with vertex . The leading coefficient is , so it opens downward and is the maximum output. Every output is at most , so the range is , choice A. Choice B () reverses the inequality, which would hold for a parabola opening upward. Choice C () describes inputs, but the range is about outputs, and the function accepts every real anyway. Choice D claims every real number can be an output, but , for example, would require , which is impossible.
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