China | A Nice Algebra Problem 

10 for a=1 to 100:for b=a+1 to 101:e=(sqr(a)+sqr(b)-sqr(175))/sqr(175) 20 if abs(e) run in bbc basic sdland hit ctrl tab to copy from the results window

Last's fermat theorem says that this exists, so i can say that this exists :D

Amei!

The solution requires a and b to be nonnegative integers. How do we know if 7x^2 and 7y^2 are nonnegative integers with x+y=5, then x and y must also be nonnegative integers?