reserve x for set;
reserve a,b,c,d,e,r1,r2,r3,r4,r5,r6 for Real;
reserve V for RealLinearSpace;
reserve u,v,v1,v2,v3,w,w1,w2,w3 for VECTOR of V;
reserve W,W1,W2 for Subspace of V;

theorem Th3:
  - (a * v) = (- a) * v
proof
  thus - (a * v) = a * (- v) by RLVECT_1:25
    .= (- a) * v by RLVECT_1:24;
end;
