SAT Math Multiple Choice Question 244: Answer and Explanation
Which of the following represents the function shown?
- D. f(x) = 3(x - 2)2 + 5
Correct Answer: A
Category: Passport to Advanced Math / Quadratics
Strategic Advice: Recognizing the different forms of a quadratic equation can save valuable time on Test Day. Each of the answer choices is given in vertex form, so start by matching the vertex of the parabola in the graph to the correct equation.
Getting to the Answer: When a quadratic equation is written in vertex form, y = a(x - h)2 + k, the vertex is (h, k). The vertex of the parabola in the graph is (2, 5); therefore, the equation should look like y = a(x - 2)2 + 5. This means you can eliminate B and C. To choose between (A) and D, consider the value of a. The parabola in the graph opens downward, so a must be negative. This means (A) is correct.