consider v being Vector of V, w being Vector of W such that
A1: f . (v,w) <> 0. K by Th41;
reconsider B = w + (RKer f) as Vector of (VectQuot (W,(RKer f))) by VECTSP10:24;
reconsider A = v + (LKer f) as Vector of (VectQuot (V,(LKer f))) by VECTSP10:24;
(QForm f) . (A,B) = f . (v,w) by Def23;
hence not QForm f is constant by A1, Th41; :: thesis: verum