English
If eval₂ of minpoly equals zero, then eval₂ of minpolyDiv is given by the appropriate conditional expression depending on whether X maps to y.
Русский
Если eval₂ от minpoly равно нулю, то eval₂ от minpolyDiv равен соответствующему условному выражению в зависимости от того, Maps X к y.
LaTeX
$$eval₂_minpolyDiv_of_eval₂_eq_zero$$
Lean4
theorem minpolyDiv_eval_eq_zero_of_ne_of_aeval_eq_zero [IsDomain S] {y} (hxy : y ≠ x) (hy : aeval y (minpoly R x) = 0) :
(minpolyDiv R x).eval y = 0 :=
by
rw [aeval_def, ← eval_map, ← minpolyDiv_spec R x] at hy
simp only [eval_mul, eval_sub, eval_X, eval_C, mul_eq_zero] at hy
exact hy.resolve_right (by rwa [sub_eq_zero])