A straight line graph with two variables is represented by an equation such as 𝑦 = 3𝑥 – 7. The equation shows the link between the 𝑥 and 𝑦-coordinates.

The constant term in the equation (the + 1 or ‒ 2) shows the point where the graph crosses the y -axis. This is known as the y -intercept and is represented by the letter c in y = m x + c.