How to find the equation of a line from a graph?

Location of two points that lie on the line is needed to define an equation of the line. The general equation of a line is in the form y = mx + c, where m is the gradient of the line and c is the y coordinate of the point where the line intercepts the y-axis. Gradient (slope) is defined as the change in Y/ change in X. We substitute the gradient of our line for m and the y coordinate of the y-axis intercept for c to get the equation of the line. When a value of an x coordinate of a point is substituted for x in the equation, the result that we will get after solving for y is the y coordinate of a point that lies on the line.