reserve x for set,
  D for non empty set,
  k,n,m,i,j,l for Nat,
  K for Field;
reserve n,i,j for Nat;
reserve n for Nat;

theorem
  for x being FinSequence of REAL, A being Matrix of n,REAL st n>0 & len
  x=n holds (A@)*x = x*A
proof
  let x be FinSequence of REAL,A be Matrix of n,REAL;
A1: len A=n & width A=n by MATRIX_0:24;
  assume n>0 & len x=n;
  hence thesis by A1,MATRIXR1:52;
end;
