Question

If X^6-Y=9999, what are the values of X and Y?

Answer 1

The permissible values of X and Y that fit your constraint, will need to meet the following criterium:

x^6 - y = 9999, so
x^6 = 9999 + y, so
x^6 -9999 = y.

Every combination of (x,y) that fits this function is acceptable.