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The Equation y = mx + c — Quick Reference

Part of Linear Graphs Problems — GCSE Mathematics

This key facts covers The Equation y = mx + c — Quick Reference within Linear Graphs Problems for GCSE Mathematics. Revise Linear Graphs Problems in Graphs for GCSE Mathematics with 16 exam-style questions and 11 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 2 of 10 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 2 of 10

Practice

16 questions

Recall

11 flashcards

The Equation y = mx + c — Quick Reference

  • m (gradient): rate of change — how steep the line is (rise ÷ run)
  • c (y-intercept): starting value — where the line crosses the y-axis
  • Positive m: line rises from left to right
  • Negative m: line falls from left to right (quantity is decreasing)
  • Finding m from two points: m = (y₂ − y₁) ÷ (x₂ − x₁)

Keep building this topic

Read this section alongside the surrounding pages in Linear Graphs Problems. That gives you the full topic sequence instead of a single isolated revision point.

Lines in the Real WorldFinding the Equation of a LineSolving Simultaneous Equations GraphicallyReal-Life Linear Graphs — Interpreting Context

Practice Questions for Linear Graphs Problems

A taxi company charges a fixed fee plus an amount per mile. On a cost graph (£ against miles), what does the y-intercept represent?

  • A. The cost per mile
  • B. The total cost of the journey
  • C. The fixed charge before any miles are travelled
  • D. The gradient of the line
1 markfoundation

A plumber charges according to the formula C = 40t + 30, where C is the total cost in pounds and t is the time in hours. Explain what the values 40 and 30 represent in this context.

2 marksstandard

Quick Recall Flashcards

Steps to find the equation of a line from a graph
1. Read the y-intercept (c) where line crosses y-axis 2. Choose two clear points on the line 3. Calculate gradient m = (y2 - y1)/(x2 - x1) 4. Write y = mx + c Example: crosses (0, 1), gradient 2 → y = 2x + 1
What does each letter in y = mx + c represent?
y = mx + c m = gradient (steepness of the line) c = y-intercept (where the line crosses the y-axis) Example: y = 3x + 2 has gradient 3 and crosses y-axis at (0, 2).

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Lines in the Real World

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Finding the Equation of a Line