PSAT Math Multiple-Choice Question 486: Answer and Explanation

Question: 486

Line a is shown in the xy-plane above. Assuming line b lies parallel to line a, which of the following equations could represent line b?

• A. y = – x – 2
• B. y = – x + 4
• C. y = – x + 3
• D. y = – x – 6

Correct Answer: C

Explanation:

C

The question asks for an equation that represents a line parallel to the one in the graph. A parallel line will have the same slope as the given line but a different y-intercept. The graph for this question has a y-intercept of 4 and a positive slope. Eliminate (A) and (B) which both have negative slopes. Calculate the slope of line a using the formula . The graph goes through the points (–7, 0) and (0, 4), so , which is . The answers are in y = mx + b form, in which m is the slope. Only (C) has a slope of . The correct answer is (C).