Point C C\,C has coordinates (4,c)(4, c)(4,c) and point D D\,D has coordinates (d,12)(d, 12)(d,12).
The perpendicular bisector of CD CD\,CD has equation 5y+x=405y + x = 405y+x=40.
Find c c\,c and ddd.
260 exam-style questions on Edexcel A Level Maths Straight Line Graphs, covering 5.1 y = mx + c, 5.2 Equations of Straight Lines, 5.3 Parallel and Perpendicular Lines, 5.4 Length and Area, and 5.5 Modelling with Straight Lines. Each one has a worked solution and a mark scheme showing where the marks go.