Rational function is: 
fx(x, y) = (1+2*x+3*x^2+4*x^3+5*x^4)/(6+7*x+8*x^2+9*x^3+10*x^4)
fy(x, y) = (11+12*y+13*y^2+14*y^3+15*y^4)/(16+17*y+18*y^2+19*y^3+20*y^4)
[0.0000000000, 0.0000000000] -> [0.1666666667, 0.6875000000]
[1.0000000000, 1.0000000000] -> [0.3750000000, 0.7222222222]
[10.0000000000, 10.0000000000] -> [0.4943845790, 0.7486039840]
[-10.0000000000, -10.0000000000] -> [0.5045020494, 0.7511306024]
