reserve X for BCI-algebra;
reserve x,y,z for Element of X;
reserve i,j,k,l,m,n for Nat;
reserve f,g for sequence of the carrier of X;

theorem Th7:
  Polynom (0,0,x,y) = x\(x\y)
proof
  Polynom (0,0,x,y) = (x,(x\y)) to_power (0+1) by BCIALG_2:1
    .= x\(x\y) by BCIALG_2:2;
  hence thesis;
end;
