Question

Which of the following is a counterexample to the conjecture given? Two lines are perpendicular only if the product of their slopes is -1.
A.)y=x;y=-x+1
B.)y=2x;x=2
C.)y=-x;y=x
D.)y=0;x=0

Answer 1

D

Answer 2

D
slope of y-axis is infinity
slope of x is 0
multiply them, we cannot get -1
but they are perpendicular