Finding the equation of a line

To find the equation of a line from its graph

• Find the gradient of the line, m
• Write down the value of the y-intercept, c.
• Substitute into y = mx + c

Example

   Write down the equation of the line shown

To find the gradient, use

or the gradient formula

either way, this gives m = -2

Write down  c = 2

Write down  y = mx + c

so the equation of the line is

         y = -2x + 2                       

© Alexander Forrest