# Thread:

1. ## Topologie question

Hello, I've two questions:

1) Given X a set then $\mathcal{P}(X)$ is a topology on X off ( $\mathcal{P}(X)$ being the power set of X).
Now if I take c and $c \notin X$ is $( \{c \} \bigcup X ) \bigcup \mathcal{P}(X)$ still a topology on X? ( I'd say yes because the 3 axioms work... I think, I might be wrong...).

2) Let $\{ \mathcal{T}_{\alpha}\}$ be a family of topologies on X. Show that there is a unique smallest topology on X containing all the collections $\mathcal{T}_{\alpha}$.

for 2) I thought I could take the subbase $\bigcup_{ \alpha \in A} \mathcal{T}_{\alpha}$. (Where A is a set), but if I'm right in 1) then I think there is a problem bc nothing tells me that none of the $\mathcal{T}_{\alpha}$ is not of the form of what I wrote in 1) so then it wouldn't be a subbase anymore.

So can someone give me a hit for 2) (or write the whole thing if you have time).

thanks in advance!!
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