Are the graph #y=5x+5# and # y=10x+5# perpendicular?
Perpendicular lines have a slope that is the opposite (or negative) reciprocal of the other. For example the perpendicular line of
I have graphed
In this case, it's basically that if you multiply 5 by 2, then you would get 10 (which is the second equation's slope).
Notice the lines are not perpendicular. Instead they intersect at the point (0,5)