User (login-registrate)
Maths Exercices

Determining the equation of a line from a graph

Many times, you'll have the graph of an equation shown to you and you'll need to find the equation.  This seems a very daunting task, but it's actually quite easy!

We can use the slope-intercept formula: y = mx + b

  • To find b, remember is the point when the line crosses the y axis
  • To find the value of the slope, you compute the rise over the run.

Remember you can also determine the equation of a line from its graph if you get two points of the line.

Find the equation of the line:

We can calculate m because the line goes through points (-2,0) and (0,3). That is .
We can calculate b because the y-intercept point is (0,3). That is b=3.
The equation of the line is: .


The equation of the line graphed in the accompanying figure is:

y= x+

If you cannot see the pictures, you must install the Plug-in from Java - Click here to download