Question 431438
{{{x^2 + y^2 = 1}}} is non-linear but does not have a 1 to 1 relation.
-----------------
y = x^2
x...y
0...0
1...1
2...4 etc.
-----------
x*y = 10 is another
x...y
1...10
2...5
5...2 
100 0.1 etc.