# Help with exponential equation

I need help creating an algorithm that outputs a number that is very slightly exponentially increasing.

Let's say I have two sets of numbers each with two variables:

Set 1

X: 15000; Y: 500


Set 2

X: 5; Y: 0.16667


I need an algorithm that will output a number, but when you increase Y, it exponentially grows.

For example, if the number outputted for Set 1 was 200 and then you changed the Y value to 800, but kept the X value the same, it should now output 400. This is just a rough example to get the point across.

I need the algorithm to output the same exact number for any set of numbers (x and y) that is put into it as long as their ratio is equal. i.e: 15000 / 500 = 5 / 0.16667

Would anyone know how I could create an algorithm that does this?

$f(x,y)=e^{\frac{y}{x}}$ should work