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Yes. Let X$X$ be finite and Hausdorff. It is enough to show that every point x$x$ in X$X$ is open. For every point y$y$ different from x$x$, there is an open neighborhood U_y$U_{y}$ of x$x$ not meeting y$y$. The intersection of the U_y$U_{y}$'s is open and equals {x}$\left\{ x\right\}$.

Yes. Let X be finite and Hausdorff. It is enough to show that every point x in X is open. For every point y different from x, there is an open neighborhood U_y of x not meeting y. The intersection of the U_y's is open and equals {x}.

Yes. Let $X$ be finite and Hausdorff. It is enough to show that every point $x$ in $X$ is open. For every point $y$ different from $x$, there is an open neighborhood $U_{y}$ of $x$ not meeting $y$. The intersection of the $U_{y}$'s is open and equals $\left\{ x\right\}$.

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David Rydh
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Yes. Let X be finite and Hausdorff. It is enough to show that every point x in X is open. For every point y different from x, there is an open neighborhood U_y of x not meeting y. The intersection of the U_y's is open and equals {x}.