let V be RealLinearSpace; for u, w, v being VECTOR of V st {u,w,v} is linearly-independent & u <> v & u <> w & v <> w holds
{u,w,(- v)} is linearly-independent
let u, w, v be VECTOR of V; ( {u,w,v} is linearly-independent & u <> v & u <> w & v <> w implies {u,w,(- v)} is linearly-independent )
- v = (- 1) * v
by RLVECT_1:29;
hence
( {u,w,v} is linearly-independent & u <> v & u <> w & v <> w implies {u,w,(- v)} is linearly-independent )
by Th30; verum