simp only [rst_iso, b2, b4, b6]
R : Type u
inst✝ : CommRing R
r s t : R
e : Model R
⊢ b6 (rst_iso r s t e) = b6 e + 2 * r * b4 e + r * r * b2 e + 4 * r * r * r
R : Type u
inst✝ : CommRing R
r s t : R
e : Model R
⊢ (e.a3 + r * e.a1 + 2 * t) * (e.a3 + r * e.a1 + 2 * t) +
      4 * (e.a6 + r * e.a4 + r * r * e.a2 + r * r * r - t * (e.a3 + t + r * e.a1)) =
    e.a3 * e.a3 + 4 * e.a6 + 2 * r * (e.a1 * e.a3 + 2 * e.a4) + r * r * (e.a1 * e.a1 + 4 * e.a2) + 4 * r * r * r