Esempi 
1/(x^2+y^2-1)=x ; y=3*x+2 ;
x=2+y^2  ;
x=3*sin(y)/y; y=sqrt(x^2+2) ;
y^2=x^2+2;
(x+5)^2/4+(y-3)^2/9=1 ;
sin(x*y)=0.5 ;
(x^2+y^2-1)^3=x^2*y^3 cuoricino