Problem 1
a) y = 8 and c) x = 2 are perpendicular lines to one another. The first is horizontal and the second is vertical.
The other two lines are not perpendicular because their slopes (1/8 and 8) do not multiply to -1. This rule only applies to lines that are neither horizontal nor vertical.
Answers: A and C.
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Problem 2
Equations b) y = (-1/2)x - 4 and c) y-4 = 2(x+3) are perpendicular. Equation B has a slope of -1/2, while equation C has a slope of 2. Those two values multiply to -1. One slope is the negative reciprocal of the other. It might help to think of 2 as 2/1.
The other two equations are not perpendicular to each other, nor are they perpendicular to B or C. Equation A has a slope of 0. Equation D has a slope of -2.
Answers: B and C
