# open/closed (3)

#### dwsmith

##### Well-known member
All numbers of the form $(-1)^n/[1 + (1/n)]$, $n\in\mathbb{Z}^+$.

$(-1)^n/[1 + (1/n)] = (-1, 1)$ is that true?

#### CaptainBlack

##### Well-known member
All numbers of the form $(-1)^n/[1 + (1/n)]$, $n\in\mathbb{Z}^+$.

$(-1)^n/[1 + (1/n)] = (-1, 1)$ is that true?
For what $n\in\mathbb{Z}^+$ does $-2/3=(-1)^n/[1 + (1/n)]$

CB

#### dwsmith

##### Well-known member
So the accumulation points are 1 and -1 and the set is open then.