題組內容
2 Let $U_k$ be a sequence of open bounded sets in $\mathbb{R}^n$. Prove or disprove:
b. (5) $\bigcap_{k=1}^{\infty} U_k$ is open.
2 Let $U_k$ be a sequence of open bounded sets in $\mathbb{R}^n$. Prove or disprove:
b. (5) $\bigcap_{k=1}^{\infty} U_k$ is open.