Solving a two unknown function

Is this possible with a two unknown function and a solve function to have all the couples of points that make Z=0 I mean how can I do

syms x;syms y;

Z=f(x,y);

S=solve(Z,(x,y));

S

and then get in the command window have : ans: S= [x(solution),y(solution)] or [x(solution1),y(solution1)]...

Answer 1

[Azzi Abdelmalek]

syms x y
z=x^2+2*y
sol=solve(z)

Answer 2

[Thierry]

Look, I tried to do what you say in my program here is the code (with matlab 7):

clear all; close all; clc;

U=400.0; S=120000; Phi=acos(1.0); P=S*cos(Phi); Q=S*sin(Phi);

I=S/(U*sqrt(3)); Zn=(U^2)/S; delta=20.0;

%%%%%%

syms Xd; syms Xq;

E1=sqrt(((U+Xq*I*sin(Phi))^2)+(Xq*I*cos(Phi))^2);

Eaf=(1/(2-Xq))*(E1+U*cos(delta)-(Xq/Xd)*U*cos(delta));

z=(-(3/2)*(U*Eaf/Xd)*sin(delta)+((U*U*(Xd-Xq))/(2*Xd*Xq))*sin(2*delta))-P;

S=subs(solve(z))

and what I get is a solution that is expressed with Xq variable and no Xd (and I know cause I've ploted it, that not all Xq points satisfy z equation)