clear;
R:=RealField();
Poly<x>:=PolynomialRing(R);
f:=x^3-2*x;
y:=x; 
Roots(y^2-f);
E:=EllipticCurve(f);
P1:=E![-1,-1];
P2:=E![0,0];
P3:=E![2,2];
P1+P2;
P2+P3;
P1+P3;
P2+P2;
y:=-1/2*x-3/2;
Roots(y^2-f); 
2*P1;
