Question

Find the slope of the line passing through each of the following pairs of points.

(−3, 9), (−3, −5)
(5, 6), (3, 4)
(0, 7), (0, −8)

(4, 0), (−2, 8)

Answer 1

Look carefully at the first pair: (−3, 9), (−3, −5) Note that x does not change, tho' y does. This is how we recognize a vertical line (whose slope is undefined). The equation of this vertical line is x = -3.

Looking at the second pair: from (3,4) to (5,6), x increases by 2 and y by 2; thus, the slope is m = rise/run = 2/2 = 1.

Third pair: as was the case with the first pair, x does not change here, and thus the equation of this (vertical) line is x=0 (which is the y-axis). The slope is undefined.