IGCSE Maths / Graphs of straight lines
Perpendicular lines
Edexcel International GCSE Maths (4MA1), chapter 6: Graphs of straight lines, specification point 3.3g. Part of the full course.
Read the revision notes · IGCSE Maths past papers
Perpendicular lines cross at a right angle, and their gradients multiply to −1. To find a perpendicular line’s equation, find its gradient, use the given point to work out c, then check the gradients.