A method of graphing a linear equation uses the Y-Intercept and the slope to create a line. Use a third point to check your work.

For example, if you want to plot f(x)=2x+1, the Y-intercept is to calculate f(0)=1 which is the height of the function at cero. The slope is the coefficient that multiply x, which in this case is 2. A third point could be evaluate at x=1 to obtain f(1)=3. So you have two positions in the cartesian plane: (0,1) and (1,3), which determine an unique line of slope 2.