# Math Help - Proving lines are perpendicular

1. ## Proving lines are perpendicular

Please tell me how to solve this problem. I would really appreciate it.

P1: 2y-x=2
P2 y+2x=4

How would you prove that they are perpendicular?

2. Hint: When you multiply the gradients of 2 perpendicular lines, the it comes to -1.