想請問 在自己定義的一個空間下
不知道這樣的證明過程是否正確
想請各問大大幫幫忙 感謝感謝
M is a topology spaces
defined by
for every countable subset F of X
and every y 不屬於 F
there exists a set U containing F and disjoint form
{y} such that U is either open or closed.
A is subset of B, B is M topology spaces
A is M topology spaces ?
Ans:
let F is countable subset of A and y不屬於 F
∵ A is subset of B and B is M
∴ F is subset of B and
exists U containing F and U∩{y}=Φ
s.t U is either open or closed
take G=U∩A
∴ G containing F and G∩{y}=Φ
s,t G is either open or closed.
So A is M topology spaces
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