let R be Ring; :: thesis: for V being RightMod of R
for L1, L2 being Linear_Combination of V st L1 + L2 = ZeroLC V holds
L2 = - L1
let V be RightMod of R; :: thesis: for L1, L2 being Linear_Combination of V st L1 + L2 = ZeroLC V holds
L2 = - L1
let L1, L2 be Linear_Combination of V; :: thesis: ( L1 + L2 = ZeroLC V implies L2 = - L1 )
assume A1: L1 + L2 = ZeroLC V ; :: thesis: L2 = - L1
let v be Vector of V; :: according to RMOD_4:def 8 :: thesis: L2 . v = (- L1) . v
(L1 . v) + (L2 . v) = (ZeroLC V) . v by A1, Def9
.= 0. R by Th18 ;
hence L2 . v = - (L1 . v) by RLVECT_1:6
.= (- L1) . v by Th50 ;
:: thesis: verum