SAT Math Multiple Choice Practice Question 475: Answer and Explanation
16. The graph of which of the following equations is parallel to the line with equation y = -3x - 6?
A. x - 3y = 3
B. x - y = 2
C. x + y = 4
D. x + y = 5
E. x + 3y = 6
Correct Answer: D
D Lines that are parallel have the same slope. In the form y = mx + b, m is the slope. So, the slope is ?3. Find the line that has a slope of ?3 when you rewrite it in the form y = mx + b. Only D works when you rewrite it: Subtract x from both sides to get y = 5 ? x, then multiply both sides by 3 to get y = 15 – 3x or y = –3x + 15.