let M1, M2 be Matrix of COMPLEX; :: thesis: ( len M1 = len M2 & width M1 = width M2 & M2 - M1 = M2 implies M1 = 0_Cx ((len M1),(width M1)) )
assume that
A1: ( len M1 = len M2 & width M1 = width M2 ) and
A2: M2 - M1 = M2 ; :: thesis: M1 = 0_Cx ((len M1),(width M1))
(COMPLEX2Field M2) + (COMPLEX2Field M1) = COMPLEX2Field M2 by A1, A2, MATRIX_4:22;
hence M1 = 0_Cx ((len M1),(width M1)) by A1, MATRIX_4:6; :: thesis: verum