I have the following case : (picture linked to the tocpic).
Let's suppose that i have two points with their value on y-axis equals to -20.5 and -19.5. I also know their value on x-axis (let's suppose 10^9 and 2*10^9). I don't have more points between them.
I would like to know : How can I find the value on X-axis of the point that have the value on y-axis equal to -20.
If it's not understandable, I hope the picture linked to it will be helpful !
Thanks you very much !