Type in the values for a,b, and, c and the equation will graph. If you want to graph a linear equation just set a as 0. To change the color of a line, you must change it with the slider before you graph the line. To toggle the visibility of the variable values just click space. You can graph multiple equations on this, the variables will be from the latest graphed equation.
Note: If the equations line won't fit the space given then it will not finish the graph properly. Also don't put fraction values, only decimals or whole numbers.