Basic Analysis I — Real Analysis · Problem 2.2.12

Sequences and Series — Jiri Lebl

Mathematics — Real Analysis · continuity-of-algebraic-operations

Problem

Let {an}n=1∞\{a_n\}_{n=1}^\infty and {bn}n=1∞\{b_n\}_{n=1}^\infty be sequences. a) Suppose {an}n=1∞\{a_n\}_{n=1}^\infty is bounded and {bn}n=1∞\{b_n\}_{n=1}^\infty converges to 00. Show that {anbn}n=1∞\{a_n b_n\}_{n=1}^\infty converges to 00. b) Find an example where {an}n=1∞\{a_n\}_{n=1}^\infty is unbounded, {bn}n=1∞\{b_n\}_{n=1}^\infty converges to 00, and {anbn}n=1∞\{a_n b_n\}_{n=1}^\infty is not convergent. c) Find an example where {an}n=1∞\{a_n\}_{n=1}^\infty is bounded, {bn}n=1∞\{b_n\}_{n=1}^\infty converges to some x≠0x \neq 0, and {anbn}n=1∞\{a_n b_n\}_{n=1}^\infty is not convergent.

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