theorem
  vector(LC_Z_Module(V),L1) - vector(LC_Z_Module(V),L2) = L1 - L2
  proof
    - L2 in LinComb(V) by Def29; then
A1: - L2 in LC_Z_Module(V);
    - vector(LC_Z_Module(V),L2) = - L2 by Th49
    .= vector(LC_Z_Module(V),- L2) by A1,RLVECT_2:def 1;
    hence thesis by Th47;
  end;
