Can you decide whether two lines are perpendicular or not? Can you do this without drawing them?
Position the lines so that they are perpendicular to each other. What can you say about the equations of perpendicular lines?
How does the position of the line affect the equation of the line? What can you say about the equations of parallel lines?
Plane 1 contains points A, B and C and plane 2 contains points A and B. Find all the points on plane 2 such that the two planes are perpendicular.