reserve i,i1,i2,i3,i4,i5,j,r,a,b,x,y for Integer,
  d,e,k,n for Nat,
  fp,fk for FinSequence of INT,
  f,f1,f2 for FinSequence of REAL,
  p for Prime;
reserve fr for FinSequence of REAL;
reserve fr,f for FinSequence of INT;
reserve b,m for Nat;

theorem Th9:
  a^2 is_quadratic_residue_mod m
proof
  (a^2 - a^2) mod m = 0 by INT_1:73;
  hence thesis;
end;
