reserve a,b,c,h for Integer;
reserve k,m,n for Nat;
reserve i,j,z for Integer;
reserve p for Prime;

theorem
  { [x,y,z] where x,y,z is negative Integer: 4*x*y-x-y = z^2 } is infinite
  proof
    dom f = NATPLUS by PARTFUN1:def 2;
    hence thesis by Th96,CARD_1:59;
  end;
