MATH2215 Mathematical Analysis Assignment 3
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MATH2215 Mathematical Analysis
Assignment 3
Scan your assignment into a single PDF file. Submit it through Moodle before 7:00p.m. on March 3, 2022 (Thursday).
You may use any result covered in lecture notes from Chapter 0 to Chapter 3 and the following theorem and definition for this assignment. However, if you use anything else, you must include in a full proof of the result that you are using.
1. Prove by ϵ-N method that the following sequences converge to the proposed limit.
(a) lim(1 + ) = 1.
(b) lim = − .
(c) lim( − ) = 0.
2. Show that lim n2 = +∞ .
3. Suppose b > 0. Define a sequence (an) by a1 = k and an+1 = (a + b)/(2an) for n ∈ N. Clearly an > 0, ∀n ≥ 2.
(a) For any fixed k, show that a ≥ b for n ≥ 2.
(b) Prove that (an) is a decreasing sequence. Thus (an) converges.
(c) Find lim an .
4. Let an ≥ 0 for all n ∈ N. Show that if (an) → 0, then ( → 0.
5. (a) Use binomial theorem to show that
2n = (1 + 1)n ≥ n(n − 1)(n − 2)(n − 3) ,
for n ≥ 4.
(b) Use ϵ-N method to show that lim = 0.
∞ ∞
6. The series P an and P bn are convergent with the inequality
n=1 n=1
an ≤ cn ≤ bn , ∀n ∈ N.
∞
Show that P cn also converges.
n=1
7. Let
B =
Answer the following items without explanation.
(a) Find the limit points of B .
(b) Is B a closed set?
(c) Is B an open set?
n ∈ N .
(d) Does B contain any isolated point? Find all isolated points of B if any.
(e) Find B, the closure of B .
2022-02-24