Key Takeaways A linear relationship, when graphed, creates a straight line. Linear relationships can be expressed either in a graphical format or as a mathematical equation of the form y = mx + b.

Revise how to plot a linear equation graph. Learn how to read x and y coordinates from a graph in this BBC Bitesize maths KS3 guide.

Well, if I know all the x and y data points, I can just calculate m and then b (since I left b in terms of m). If I don't have too many data points, I could do this by hand.