Cauchy and limit superior

Suppose that {a_n}_n is a real Cauchy sequence. Prove that lim superior n--> infinity (a_n) = lim inferior n--infinity (a_n) so as to conclude that lim n--infinity (a_n) exists.

sup question

Suppose the sequences {a_n}_n and {b_n}_n are both bounded above. a) Prove that for all n in the naturals sup{a_k + b_k: k>/=n} is less than or equals sup{a_k:k>/=n} + sup{b_k:k>/=n} b) Use this to conclude: limsup (a_n + b_n) is less than or equals limsup(a_n) + limsup(b_n) (all limits are n--> infinity)

sequence and supremum

Suppose that the sequences {a_n}_n is bounded above and lim(b_n) exists. a) Prove that for all e>0 there is an N st that for all n>=N sup{a_k:k>=n} + b_n <=sup{a_k + b_k: k>=n} + e. b) Use this to conclude limsup(a_n) + lim (b_n) <= limsup (a_n+b_n) (all limits are n ---> infinity)

series convergence

Suppose the summation from k=1 to n of a_k is absolutely convergent and {b_n} is bounded. Prove that this implies the summation from k=1 to n of a_k*b_k is absolutely convergent.

iteration scheme

Consider the real number iteration scheme x_n+1 = f(x_n) for n = 1, 2, ... with x_1 given. In addition, suppose there is a number 0 < p < 1 st lf(x) - f(y)l < = plx-yl for all x,y. a) Show lx_n+1 - x_nl < = p^n-1lx_2 - x_1l for all n. b) From this, conclude {x_n}_n is Cauchy.