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#### OhMyMarkov

##### Member

- Mar 5, 2012

- 83

I'm trying to prove that the closure of $A = [-\infty,0)$ is $[-\infty,0]$. So far, I have proved that all points in $[-\infty, 0)$ are limit points of A, then I have proved that $\sup A = 0$, so it is in the closure, so $[-\infty, 0]$ subsets the closure.

But how do I know that it is equal to the closure?