2. Suppose that (an), İs a sequence of complex numbers such that there exists a positive number 0...
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....
#s 2, 3, 6 2. Let (En)acy be a sequence in R (a) Show that xn → oo if and only if-An →-oo. (b) If xn > 0 for all n in N, show that linnAn = 0 if and only if lim-= oo. 3. Let ()nEN be a sequence in R. (a) If x <0 for all n in N, show that - -oo if and only if xl 0o. (b) Show, by example, that if kal → oo,...
Problem 6) (The Cauchy condensation test] Let {an} be a nonincreasing sequence of positive numbers (an > an+1 for all n) that converges to 0. The Cauchy condensation test states that Dan converges if and only if 2"2n converges. For example, 1/n diverges because 2" (1/2") = 1 diverges. Explain why the test works.
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...
(2) (a) Let {n}nen be a sequence of complex numbers. Show that if lim, toon = 2, then lim 21+z2+ + + Zn 100 (b) Using (a), find the limit limn7 (m_ +i i zm).
2) Suppose that {ễnhei be a sequence of positive numbers for which s rsn for some r E (0,1). Prove that this sequence converges to zero. <
Problem 2 Show that if the sequence of numbers (an)n-1 satisfies Inlan) < oo, then the series In ancos(nx) converges uniformly on [0, 27). This means, the partial sums Sn(x) = ) ancos(nx) define a sequence of functions {sn} = that converges uniformly on [0, 271]. Hint: First show that the sequence is Cauchy with respect to || · ||00.
4. Suppose (fr)nen is a sequence of functions on [0, 1] such that each fn is differentiable on (0,1) and f(x) < 1 for all x € (0,1) and n e N. (a) If (fn (0))nen converges to a number A, prove that lim sup|fn(x) = 1+|A| for all x € [0, 1]. n-too : (b) Suppose that (fr) converges uniformly on [0, 1] to a function F : [0, 1] + R. Is F necessarily differentiable on (0,1)? If...
Example: Let {xn} be a sequence of real numbers. Show that Proposition 0.1 1. If r is bounded above, x = lim sup (r) if and only if For all 0 there is an NEN, such that x <x+e whenevern > N, and b. For all >0 and all M, there is n > M with x - e< In a. Example: Let {xn} be a sequence of real numbers. Show that Proposition 0.1 1. If r is bounded above,...
6. Suppose that {x,] is a sequence of positive numbers and limA = a Show that if L> 1 then lim x =00, and if L < 1 lim x = 0 n+02 b. Construct a sequence of positive numbers {x,} such that lim * = 1 and the sequence {x} diverges. c. Let k E N and a > 1 Show that lim = 0. O LIVE