reserve m,n for Nat;
reserve i,j for Integer;
reserve S for non empty addMagma;
reserve r,r1,r2,s,s1,s2,t,t1,t2 for Element of S;
reserve G for addGroup-like non empty addMagma;
reserve e,h for Element of G;
reserve G for addGroup;
reserve f,g,h for Element of G;

theorem Th16:
  -(h + g) = -g + -h
proof
  (-g + -h) + (h + g) = -g + -h + h + g by RLVECT_1:def 3
    .= -g + (-h + h) + g by RLVECT_1:def 3
    .= -g + 0_G + g by Def5
    .= -g + g by Def4
    .= 0_G by Def5;
  hence thesis by Th11;
end;
