Practice Final Examination 2 – Math 142B
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
Practice Final Examination 2 – Math 142B
Question 1. Determine whether each of the following statements is true or false. No justification is required.
(a) |
If an > 0 for all n and liminf |an+1|/|an | < 1, then 对 an converges. |
|
(b) |
If 对 an converges, then 对 sin(an ) converges. |
|
(c) |
If f(x) = 对 anxn converges for x ∈ [−r,r], then for x ∈ [−r,r], f\ (x) =对 nanxn−1 . |
|
(d) |
For |x| < 1, 对 = x − log(1 − x). |
|
(e) |
The coefficient of x4 in the Taylor series for eex about x = 0 is 5e/8. |
|
(f) |
Let fn and f be differentiable on [0, 1]. If fn → f uniformly on [0, 1], then f → f\ uniformly on [0, 1]. |
|
(g) |
Let f(x) be the smallest integer larger than 2sin x where 0 ≤ x ≤ π . Then f is integrable on [0,π]. |
|
(h) |
Let f(x) = sin() for x 0 and f(0) = 0. Then l1 f does not exist. |
|
(i) |
Let fn : [0, 1] → R be integrable, and suppose fn → 0 pointwise for x ∈ [0, 1]. Then limn→∞ l01 fn = 0. |
|
(j) |
Le ϵ > 0. If f is an integrable function on [0, 1] and P is the partition with parts [ , ] where 0 ≤ i < n, then U(f,P) − L(f,P) < ϵ provided n is large enough. |
|
Question 2. Let fn (x) = (x + n)/(1 + nx3 ) for x > 0 and n ≥ 1
(a) Determine a function f such that fn → f pointwise for x > 0. (b) Is the convergence in (a) uniform on (0, 1]?
(c) Is the convergence in (a) uniform on [1, ∞)?
Question 3.
Let f(x) = xex for x ∈ [0, 1].
(a) Determine the nth Bernstein polynomial fn (x) for f where n ≥ 1. (b) Prove that fn (0) = 0 and fn (1) = e for all n ≥ 1.
(c) Prove that sup{|fn (x) − f(x)| : x ≥ 0} → ∞ as n → ∞ .
Question 4.
For n ≥ 1 and x ∈ [0, 1], let
sin(log(1 + x))
1 + x + xn
(a) Prove that f1 (x) ≤ f2 (x) ≤ ... for all x ∈ [0, 1]. (b) Determine a function f such that fn → f pointwise on [0, 1]. (c) Prove that fn (x) is integrable on [0, 1] for all n ≥ 1. (d) Prove that f is integrable on [0, 1].
(e) Determine the value of
n(l) \0 1 fn (x)dx.
2022-09-01