Edexcel IGCSE Maths topic guide

Graphs and Coordinate Geometry

Graph questions connect equations to shape and position. Marks commonly depend on an accurate scale, plotted points, a clearly shown gradient calculation and a conclusion that uses the graph rather than guesswork.

Foundation and Higher relevance

Foundation and Higher both use coordinates and straight-line graphs. Higher work adds more demanding transformations, tangents and interpretation of non-linear graphs.

Topic coverage

Coordinates and plotting
Linear graphs
Straight lines in the form y = mx + c
Quadratic, cubic and reciprocal graphs
Gradients and intercepts
Equations of straight lines
Real-life and travel graphs
Graph transformations

Worked example

Question: Find the equation of the line through (2, 3) and (6, 11).

Calculate the gradient: (11 − 3) ÷ (6 − 2) = 8 ÷ 4 = 2.
Use y = mx + c with (2, 3): 3 = 2(2) + c.
Solve for c: c = −1.

Answer: y = 2x − 1.

Common errors

Dividing the change in x by the change in y when finding gradient.
Reading coordinates from an inconsistent or unlabelled scale.
Using a point that does not lie on the requested line or tangent.

Revision checklist

I label axes and use a consistent scale.
I can calculate gradient from two points in the same order.
I can recognise linear, quadratic, cubic and reciprocal graph shapes.