Line A has the equation 3x + y = 7. Which of the following lines is perpendicular to Line A?  Choose the correct choice from the following answers:
A) y = 3x + 4  B) y = –3x – 6  C) y = (1/3)x – 1  D) y = (–1/3)x + 2  E) y = (–7/3)x – 5
What’s tricky about this problem: we have to begin by solving the given equation for y, so that we know its slope.   The slope of the original line is m = –3, and the negative reciprocal of that is +1/3, so the perpendicular line must have a slope of +1/3. Among the answer choices, the only line with a slope of +1/3 is (C).   Answer y = (1/3)x – 1
<result>C</result>
Line A has the equation 3x + y = 7. Which of the following lines is perpendicular to Line A?