theorem
  b <> 0 & c <> 0 implies (r*b+c) / b > r
  proof
    assume that
A1: b <> 0 and
A2: c <> 0;
A3: (r*b+c) / b = r*b/b + c/b
    .= r + c/b by A1,XCMPLX_1:89;
    r + c/b > r + 0 by A1,A2,XREAL_1:8;
    hence thesis by A3;
  end;
