Consider the lines
y = 3x + 5
2y = 4x + 5
3y = x - 2
2y = 3x - 2
4y = x - 5
Let's say that a pair of lines is good if the two lines are either parallel or perpendicular to each other. Among all the pairs of lines shown, how many pairs are good?
See here : https://web2.0calc.com/questions/please-help_45967
