English
If b divides a − r with deg r < m and a,b are monic of degrees m,n respectively, then there exists q monic of degree m − n with a = q b + r.
Русский
Если b делит a − r и deg r < m, и a,b моноичны степеней m и n соответственно, то существует q моноичны степени m − n с a = q b + r.
LaTeX
$$$\\exists q:\\, IsMonicOfDegree\\ q (m-n) \\land a = q \\cdot b + r$$$
Lean4
theorem of_dvd_sub {a b r : R[X]} {m n : ℕ} (hmn : n ≤ m) (ha : IsMonicOfDegree a m) (hb : IsMonicOfDegree b n)
(hr : r.natDegree < m) (h : b ∣ a - r) : ∃ q : R[X], IsMonicOfDegree q (m - n) ∧ a = q * b + r :=
by
convert ha.of_dvd_add hmn hb ?_ h using 4 with q
· rw [sub_neg_eq_add]
· rwa [natDegree_neg]