English
For each n, the image of the n-th derived subgroup under a group hom f satisfies f(derivedSeries(G,n)) ≤ derivedSeries(G',n).
Русский
Образ n-го члена производящей серии под гомоморфизмом f удовлетворяет f(derivedSeries(G,n)) ≤ derivedSeries(G',n).
LaTeX
$$(\\mathrm{derivedSeries}(G,n)).map f \\le \\mathrm{derivedSeries}(G',n)$$
Lean4
theorem map_derivedSeries_le_derivedSeries (n : ℕ) : (derivedSeries G n).map f ≤ derivedSeries G' n := by
induction n with
| zero => exact le_top
| succ n ih => simp only [derivedSeries_succ, map_commutator, commutator_mono, ih]