How do you find the equation of perpendicular lines?

First find the equation of one line using the information you have.

• You may need to use the formula for finding gradient, then find the intercept using a known point that the line passes through.

If your first line has equation y = mx + c then a line that is perpendicular will have a gradient equal to -1/m

You can find the intercept of the second line by plugging in any known value on that line.