The equation of a straight line graph is: y = m x + c https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429294402/b9ca5d79-2df6-4df2-84c0-1127de132c67/content/eq1941.tif"/> where m is the gradient and c the y-axis intercept.