Edexcel IGCSE Maths 复习笔记 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!