English
The GP-free property remains unchanged under scalar multiplication, i.e., ThreeGPFree(a•s) is equivalent to ThreeGPFree(s).
Русский
Свойство GP-free сохраняется при умножении множества на скаляр; ThreeGPFree(a•s) совпадает с ThreeGPFree(s).
LaTeX
$$$ThreeGPFree(a\cdot s) \iff ThreeGPFree(s)$$$
Lean4
@[to_additive]
theorem threeGPFree_smul_set : ThreeGPFree (a • s) ↔ ThreeGPFree s
where
mp hs b hb c hc d hd
h :=
mul_left_cancel
(hs (mem_image_of_mem _ hb) (mem_image_of_mem _ hc) (mem_image_of_mem _ hd) <| by
rw [mul_mul_mul_comm, smul_eq_mul, smul_eq_mul, mul_mul_mul_comm, h])
mpr := ThreeGPFree.smul_set