几道判断题
1 a homomorphism is an infection and a surjection
2 the character of an intergral domain is prime or zero
3 A4 have subgroup of order 6 and 12
第三题就是A4是否有6阶和12阶的子群呗~
a homomorphism is not necessarily an infection, nor is it necessarily a surjection.同态不一定是单射,也不一定是满射(同态一旦既是单射又是满射,它就是同构了);
the character of an intergral domain is not necessarily prime or zero(整环的特征未必是素数或0);
A4 doesn't have any subgroup of order 6(A4没有6阶子群),可以百度“交代群A4没有6阶子群”看看。
也谢谢你~还有 几个问题
the character of Z6 is 0
the kernel of a ring homomorphism is an ideal
every group is a permutation group up to an isomorphism.
不过你设置了不能向你提问。
不必谢我。但上面的答案是错误的,请注意不要被误导了!
后面几个如果是要证明的习题,建议你认真看讲义,只要把概念弄清楚了,这些都是很简单的题目。