PSAT Math Multiple-Choice Question 25: Answer and Explanation

Question: 25

Line l is shown in the graph above. If line m is parallel to line l, which of the following could be the equation of line m?

• A. -3x - 1
• B.
• C.
• D. 3x + 2

Correct Answer: B

Explanation:

B

The question asks for the equation of a line that is parallel to a line shown in a graph. Parallel lines have equal slopes. Therefore, because the line in the graph has a negative slope, the correct answer will also have a negative slope. Eliminate (C) and (D) right away because they have positive slopes. Now find the exact slope of the line shown, and compare it with the remaining answers to see which line equation has the same slope. The slope of a line is determined by the equation . Calculate the slope of the line shown to get . The answers are all in the slope-intercept form of an equation, y = mx + b, where m = slope. Only (B) has a slope of . The correct answer is (B).