Question

Marisol attempted to determine the slope of a line based on the two points shown in the table below.

x
y
–1
4
3
10

Step 1: (–1, 4) and (3, 10)

Step 2: StartFraction 10 minus 3 Over 4 minus (negative 1) EndFraction

Step 3: StartFraction 7 Over 5 EndFraction

Which statement best explains Marisol’s error?
Marisol computed StartFraction y 2 minus y 1 Over x 1 minus x 2 EndFraction.
Marisol computed StartFraction x 2 minus x 1 Over y 2 minus y 1 EndFraction.
Marisol computed StartFraction y 2 minus x 2 Over y 1 minus x 1 EndFraction.
Marisol computed StartFraction x 2 minus y 2 Over x 1 minus y 1 EndFraction.

Answer 1

Marisol computed (y2 − x2) / (y1 − x1).

Explanation: With (x1,y1) = (−1,4) and (x2,y2) = (3,10) she got (10 − 3)/(4 − (−1)), which is y2 − x2 over y1 − x1 instead of the correct (y2 − y1)/(x2 − x1).