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SAMPLE QUIZ 2. MATH 216.
发布时间:2022-02-15
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SAMPLE QUIZ 2. MATH 216.
Problem 1. Let {xn } be a sequence in R such that there is θ e [0, 1) with
Ixn+l - xn I < θn
for all n e N. Show that {xn } is a fundamental sequence and therefore converges.
Problem 2. a. Let {xn } and {yn }
be two convergent sequences in R. Assume that there exists N e N such that for every n 2 N one has xn < yn . Show that
lim xn < lim yn .
b. Show that there exists two convergent sequences {xn } and {yn }
in R such that for every n 2 1 one has xn < yn but
lim xn 2 lim yn .
Problem 3. Let {xn } be a sequence in R, let x be an accumulation point of {xn }
, and let {ε亿 }
be a sequence of strictly positive reals such that lim亿 →o ε亿 = 0. Show that there is a subsequence {xnk}
of {xn }
such that Ixnk - xI < ε亿 for all k e N.