MAST20026 Real Analysis SAMPLE QUESTIONS Semester 2, 2022
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MAST20026 Real Analysis SAMPLE QUESTIONS
Semester 2, 2022
Question 1 Express each of the following statements in first-order logic.
(a) the product of an irrational number and a non-zero rational number is irrational.
(b) f(x) is bounded on [a,b]
Question 2 Give an example of a set which is a natural number, and an example of a set which is not a natural number.
Question 3 Let A and B be non-empty sets that are bounded above. Let A + B denote the set A + B = {a + b | a ∈ A b ∈ B}
Using the definition of supremum prove
supA + B ≤ supA + supB
Question 4 Let S ⊆ R. Prove that if S has a supremum, then there is exactly one element of R that satisfies the definition of supremum of S . Use the Real Number Axioms and Theorems from Section 3, where appropriate, to justify the steps in your proof.
Question 5 True or false:
(a) The set R with the usual order is well-ordered.
(b) The set N with the usual order is well-ordered.
(c) There is a continuous function f : (0, 1) → R that is not injective.
Question 6 Let (gn) be Cauchy. Using the definition of Cauchy prove there exists M ∈ N+ so that gM+1 + is an upper bound for the set
{gk | k > M}
Question 7 Let m ∈ R. Let f,g : R → R so that f(x) > g(x) for all x > m. Prove that if
lim g(x) = ∞, then lim f(x) = ∞ .
x→∞ x→∞
Question 8 Let f : R → R be a continuous function. Let c ∈ R so that f(北) > 0. Prove there exists 6 > 0 so that f(北) > 0 for all 北 ∈ (c − 6,c + 6).
Question 9 Let n ∈ N+ and let
f(x) = 2xn + xn −1 + xn −2 + ··· + x2 + x + 1 Prove that if n is odd, then f(x) has at least one root in the interval (−1, 1)
Question 10 Let f : R → R so that
x ∈ Q
x Q
Prove f is not integrable on [3, 4].
Question 11
Find the interval of convergence of the following power series.
∞
(x − 3)n
Question 12 Compute the order 2 Taylor polynomial of x2 sin x at 0.
Question 13 Let K ∈ R+ Let f : R → R be an infinitely differentiable function so that for all n ∈ N and all 北 ∈ R we have
|f(n)(北)| < K
Prove that if the Taylor series of f at 0 converges at 北, then it converges to f(北). As part of your solution you may assume the following fact
cn
n→∞ n!
for all c ∈ R.
2022-11-03