竟然會有funamental theorem of algebra
analytic proof只見過d Alembert one同Cauchy integral formula嘅corollary
但Algebra proof真係第一次見,一定要睇
Ever172025-03-22 02:38:30
當年d Alembert同Gauss無topology 呢啲工具但都好犀利
米拉·瓦勒里2025-03-22 08:57:00
CCCP2025-03-22 12:14:53
膠智的kai龍2025-03-22 12:47:37
Ever172025-03-22 14:01:25
又交返個波俾我
證p-group has all its p subgroup, order p, p^2,…p^k-1
程式猿2025-03-22 17:23:41
泰國2025-03-22 18:11:51
膠智的kai龍2025-03-22 18:41:17
唔係sylow d朋友?
Ever172025-03-22 19:41:51
係,首先假設R[i]對上仲有個finite extension E,而K就係嗰個finite extension用automorphism集合,R[i]-E-K
做做下就證到有個entire Galois group有2-Sylow subgroup存在,咁Gal(K/R) 就會係2^k,但仲有odd part。不過odd當中irreducible polynomial嘅degree有1(by IVT, all odd degree has one real root, hence only possible degree of irreducible polynomial is 1,但1,其實就等於喺R,所以其實係冇)。
證埋呢度(by induction, center, correspondnece)就可以話存在quadratic extension F,但extend嘅元素其實都係屬於R[i],因為all positive real number has root and complex number has root as well,所以F = R[i],一路用呢個argument,K=R[i],咁頭先R[i]-E-K=R[i]就要令E都係R[i],i.e. 所有arbitrary finite extension都係佢自己,咁R[i]就係algebraic closure of R,every polynomial of R has a root in R[i],i.e. C