Two unkowns calculator with graphic.

So let's take for example the highschool problems regarding lineal functions.

x=2y +1

then I have a program that makes a chart with an accuracy of 1


x y

-1 -1
0 1
1 3
2 5
3 6

Now I created a formula to calculate some poker calculations which involve 5 factors.
I want it so that if you enter 2 of these factors, it will release multiple lines (depending on the 5th factor) on a 2 axis graphic, (the 2 axis being 3rd and 4th factor.
How can I translate the chart to graphic.
What is the most effective way of programming it.