Edexcel IGCSE Maths

Revision Notes

3.6.1 Straight Lines - Finding Equations

Why do we want to know about straight lines and their equations?

  • Straight Line Graphs (Linear Graphs) have lots of uses in mathematics – one use is in navigation
  • We may want to know the equation of a straight line so we can program it into a computer that will plot the line on a screen, along with several others, to make shapes and graphics

How do we find the equation of a straight line?

  • The general EQUATION of a straight line is y = mx + c
    • where m is the gradient
    • c is the y-axis intercept
  • To find the EQUATION of a straight line you need TWO things:
    • the gradient, m
    • any point on the line
  • You might find these things from a graph, another equation or two points
  • You may be asked to give the equation in the form ax + by + c = 0
    (especially if m is a fraction)
    If in doubt, SKETCH IT!

Worked Example

Straight Lines - Finding Equations Worked Example 1, downloadable IGCSE & GCSE Maths revision notes

Sketch Parallel Lines, IGCSE & GCSE Maths revision notes

Straight Lines - Finding Equations Worked Example 2, downloadable IGCSE & GCSE Maths revision notes

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