Designing a multi-variable equation based on known output
  
 
     
     
             
                 
 
 
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 First of all, I apologize for my lack of proper math vocabulary. I'm mainly a programmer.   I need to write an equation that relates variables s  and p . ( s  is  star mass, p  is planet radius). The equation needs to roughly fit these parameters:   When s = 2, changing p between 0.01 and 2 makes the output range from 340 to 350.   When s = 1, changing p makes the output range from 0 to 150.   When s = 0.5, changing p makes the output range from 0 to 50.   s  is limited to the range 0.5 to 2, and p  is limited to 0.01 to 2.   Here's a visual representation of what I'm talking about:     --   How do I go about solving something like this? I've been doing trial and error for a little too long, so I figured I'd open up a question on here.   What I have so far is something like:   $f(s, p...