SAT Math Multiple Choice Practice Question 572: Answer and Explanation
The graph of y = f(x) is shown above. Which of the following could be the equation for f(x) ?
A. f(x) = 2x
B. f(x) = x2
C. f(x) = 2x2
D. f(x) = x - 2
E. f(x) = |2x|
Correct Answer: E
E In the graph, y is always positive. E is correct because absolute value is always positive. One way to answer this question is to plug in points from the graph into the equations in the answers. Using point (1, 2), A works because 2 = 2(1). Eliminate B because 2 does not equal 11; also, because of x2, this is a parabola, not a line. Although the point works in C, 2x2 indicates a parabola, so eliminate C. Eliminate D because 2 does not equal 1 – 2. In E 2 = 2 does work. Now try the other point from the graph just on equations A and E. A is out because 2 does not equal –2.