

41. Let (an) be a sequence of strictly positive real numbers and Sn = ak (a)...
3.) Let ak E R with ak > 0 for all k E N. Suppose Σ㎞iak converges. Show that Σί1bk (By definition, for a sequence (ck), we say liCkoo if, for all M ER with Hint: Show that there exists (Ni))ไ1 with N > Nj for all j E N, such that bk there exists a sequence (bk)k of real numbers such that lim converges = oo and M >0, there exists N E N such that ck > M...
(Exercise 4.13, reordered) Given a series ΣΧί ak, let 8,-Ση-i ak. Σχί ak is Cesaro summable if S1 + 82 +... +Sn lim n-+o converges. (a) Give an example of a series Σ00i ak that is Cesaro sum mable but not convergent (b) Prove that if 1 ak converges, then it is Cèsaro summable. Hint: Say the sequence of partial sums sn → L. Try to prove that =1 8k → L by showing and then splitting the latter sum...
(c) (5 marks) Give an example of i. a sequence of real numbers that is strictly increasing and converges to zero; ii. a sequence of real numbers that is not monotonic and converges to 2 iii. a sequence of real numbers that is bounded and divergent. (d) (5 marks) Calculate the first four terms in the Laurent series representation of e*.
(4) Let Σ ak and Σ bk be series with positive terms. The limit comparison test applies when a/bk L0; suppose for this problem that ak/bk0. (a) Show that if Σ bk converges, then Σ ak converges. Hint: remember we can delete finitely many terms from the series and not affect convergence. Use the fact a/bk0 to truncate the series at a convenient point. (b) Show that if ak diverges, then bk diverges. (c) Show by example that if Σ...
Let an, hen be a strictly monotonic sequence of real numbers with aro and the limit of 1. Let Yn be a sequence of Continuous real-valued fmetions on (0,13 with Yn 20 and Jual, so that the support of Yn is in Jan, anta [ A function f : [0,13? → R is defined as: nein | 6%9) - 2(--) -.-) . . a) Cubabe si Cinsel)aly and . (5 testube. Tip: Fix xe [an, Amen] (then overy and do...
Suppose an- is a decreasing sequence of non-negative numbers (that is, 0 S an+1 S an for all n) a) Show that 2K a1 + - n-1 b) Suppose Σ-1 an is a convergent series. Use part a to show that Σ-1 2na2n converges. HINT: recall the monotonic sequence theorem c) Show that n-1 d) Suppose that Ση_1 2na2n is a convergent series. Use part c to show that Ση-1 an e shown that Ση.1 an conv Σ-1 2na2n converges....
Problem 1 Let {ak} and {bk} be sequences of positive real numbers. Assume that lim “k = 0. k+oo bk 1. Prove that if ) bk converges, so does 'ak k=1 k=1 2. If ) bk diverges, is it necessary that ) ak diverges? k=1 k=1
Let (xn) be a sequence of strictly positive terms and let (yn) be the se- quence defined by Yn = 1 + Xn Compare the series 2n-1 Xn and -Yn regarding their convergence or divergence.
1. Let {n} be a sequence of non negative real numbers, and suppose that limnan = 0 and 11 + x2 + ... + In <oo. lim sup - n-00 Prove that the sequence x + x + ... + converges and determine its limit. Hint: Start by trying to determine lim supno Yn. What can you say about lim infn- Yn? 3 ) for all n Expanded Hint: First, show that given any e > 0 we have (...
+00 bn are series with positive terms an and (a) Suppose that O bn is convergent. Prove that if "limo and that I1 n= 1 +00 then Σ an is also convergent. (b) Use part (a) to show that the series converges t In (n)
+00 bn are series with positive terms an and (a) Suppose that O bn is convergent. Prove that if "limo and that I1 n= 1 +00 then Σ an is also convergent. (b) Use part...