Is there a formula for x that works for the following set of values for x-y? 2-15,4-30,6-50,8-65?

Answer 1

I'm sure there is, but it's a lot more work than I want to do for 2 points. For any set of data points, an equation can be devised to fit them. The more points, the screwier the formula. Four points require no more than a cubic equation.

For the coefficients for AX^3 +Bx^2 +Cx +D, solve the following matrix division:

2 2 2 2 15
4 4 4 4 30
6 6 6 6 / 50
8 8 8 8 65