The work of two students is shown for the problem: What is the slope of a line that is perpendicular to a line that passes through (–22, 13) and (17, 12)?


Student A Student B
m equals the quantity 12 minus 13 end quantity over the quantity 17 minus negative twenty two end quantity equals negative 1 over thirty nine. m equals the quantity 12 minus 13 end quantity over the quantity 17 minus negative twenty two end quantity equals negative 1 over thirty nine.
The slope of the perpendicular line is –39. The slope of the perpendicular line is 39.

Part A: Which student has the correct slope of the perpendicular line? (2 points)

Part B: Explain how the answer to Part A is correct. (2 points)