theorem Th40: :: LOPBAN_9:23

for X, Y, Z being RealNormSpace
for f, g, h being Point of (R_NormSpace_of_BoundedBilinearOperators (X,Y,Z)) holds
( h = f - g iff for x being VECTOR of X
for y being VECTOR of Y holds h . (x,y) = (f . (x,y)) - (g . (x,y)) )