Enter the equation of a line into your online or desktop graphing calculator. Use 2x + 1 for the line equation in this example. Select the graph or plot function on your graphing calculator to plot the line on the screen.
Select an arbitrary point on your line. Call that point the origin reference, or R. Assign the origin reference point a x-coordinate value of 0 and a y-coordinate value of 0. Write down the point in symbolic mathematical notation as R(0,0) for origin reference point at x-coordinate, 0, and y-coordinate, 0.
Pick an arbitrary point to the right of reference origin point, R. Call this point the terminal point, or T, for short.
Write down the horizontal distance (inches, centimeters or other units your graphing calculator is demarcated in) between the reference origin and the terminal point. Call this distance the "run."
Write down the vertical distance (inches, centimeters or other units your graphing calculator is demarcated in) between the reference origin and terminal point. Call this distance the "rise." Prefix the rise with a negative sign if the terminal point, P, is below the reference point, R.
Divide the rise, from Step 5, by the run, from Step 4, to determine the slope, m. Verify that the slope, m, you calculated is 2, which is the slope of the line equation you entered in the graphing calculator in Step 1.