4-07 rings and homomorphisms

4-09，代数如漫漫长夜，依然是实规范矩阵，酉矩阵这些的吧。

一星期没有学代数😶😶

4-17 理想之与环如正规子群之与群

4-19 幂零群都是可解群

4-26 不低于5阶的对称群都不是可解群。

5.3 奇数阶有限群都是可解群

5-12 有单位元的非零环上永远有极大理想，In fact每个理想都包含在一个极大的理想。

5-29 A local ring is a commutative ring with identity which has a unique maximal ideal. Since every ideal in a ring with identity is contained in some maximal ideal, the unique maximal ideal must contain every ideal of R(except of course R itself).

8-29 有限除环是域

9-14 群的扩张

9-17 伽罗华群

10-9 有限域的非零元素组成的乘法子群一定是循环群