
theorem Th8:
  for i,j,k being Integer st i divides j holds k*i divides k*j
proof
  let i,j,k be Integer;
  assume i divides j;
  then consider z being Integer such that
A1: i * z = j by INT_1:def 3;
  (i*k)*z = j * k by A1;
  hence thesis by INT_1:def 3;
end;
