∀ {𝕜 : Type u_2} [inst : NontriviallyNormedField 𝕜] {E : Type u_3} {F : Type u_4} [inst_1 : NormedAddCommGroup E]
  [inst_2 : NormedSpace 𝕜 E] [inst_3 : NormedAddCommGroup F] [inst_4 : NormedSpace 𝕜 F] {f : E → E →L[𝕜] F}
  {pf : FormalMultilinearSeries 𝕜 E (E →L[𝕜] F)} {s : Set E} {x : E} {z : F},
  HasFPowerSeriesWithinAt f pf s x → HasFPowerSeriesWithinAt (fun y => z + (f y) (y - x)) (pf.unshift z) s x