reserve

  k,n,m,i,j for Element of NAT,
  K for Field;
reserve L for non empty addLoopStr;
reserve G for non empty multLoopStr;

theorem Th17:
  for A,B,C being Matrix of n,K holds A*B*C=A*(B*C)
proof
  let A,B,C be Matrix of n,K;
A1: width B=n & len C =n by MATRIX_0:24;
  width A=n & len B=n by MATRIX_0:24;
  hence thesis by A1,MATRIX_3:33;
end;
