Math Core

Unit 6 · Test

Unit 6 test: Infinite Sequences and Series

15 questions. Answer them all, then submit to see your score. Solutions unlock after you submit.

This test covers sequences, the nth term test, geometric series, the integral, p-series, comparison, alternating series and ratio tests, absolute and conditional convergence, Taylor polynomials, the Lagrange error bound, intervals of convergence, Taylor and Maclaurin series, and working with power series.

Question 1

Find lim⁡n→∞4n3−n6n3+5n2\displaystyle\lim_{n\to\infty} \frac{4n^3 - n}{6n^3 + 5n^2}.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 2

What can be concluded about ∑n=1∞3n−15n+2\displaystyle\sum_{n=1}^{\infty} \frac{3n - 1}{5n + 2}?

Question 3

Find the sum of ∑n=1∞6(37)n\displaystyle\sum_{n=1}^{\infty} 6\left(\frac{3}{7}\right)^n.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 4

The integral test is applied to ∑n=1∞1(2n+1)2\displaystyle\sum_{n=1}^{\infty} \frac{1}{(2n + 1)^2}. Which is the correct conclusion?

Question 5

Which of the following series converges?

Question 6

To apply the limit comparison test to ∑n=1∞n2+32n4−n\displaystyle\sum_{n=1}^{\infty} \frac{n^2 + 3}{2n^4 - n}, it is compared with ∑1n2\displaystyle\sum \frac{1}{n^2}. Find lim⁡n→∞anbn\displaystyle\lim_{n\to\infty} \frac{a_n}{b_n}.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 7

The series ∑n=1∞(−1)n+1n2\displaystyle\sum_{n=1}^{\infty} \frac{(-1)^{n+1}}{n^2} is approximated by S5S_5, the sum of its first five terms. Using the alternating series error bound, find the best upper bound on the error.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 8

For ∑n=1∞n3 2n5n\displaystyle\sum_{n=1}^{\infty} \frac{n^3\, 2^n}{5^n}, find the ratio test limit L=lim⁡n→∞∣an+1an∣L = \displaystyle\lim_{n\to\infty}\left|\frac{a_{n+1}}{a_n}\right|.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 9

Classify ∑n=2∞(−1)nnln⁡n\displaystyle\sum_{n=2}^{\infty} \frac{(-1)^n}{n \ln n}.

Question 10

A function ff has f(3)=1f(3) = 1, f′(3)=−2f'(3) = -2, f′′(3)=5f''(3) = 5 and f′′′(3)=6f'''(3) = 6. Write the third-degree Taylor polynomial for ff about x=3x = 3.

Enter an expression, e.g. 3x^2 - 2x + 1

Question 11

A function gg has derivatives of all orders and satisfies ∣g(5)(x)∣≤12|g^{(5)}(x)| \le 12 on [0,0.5][0, 0.5], and its fourth-degree Maclaurin polynomial is used to approximate g(0.5)g(0.5). Find the Lagrange error bound.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 12

Find the interval of convergence of ∑n=1∞(−1)n(x+1)nn 2n\displaystyle\sum_{n=1}^{\infty} \frac{(-1)^n (x + 1)^n}{n\,2^n}.

Enter an inequality, e.g. x >= 4, -2 < x <= 3, or x < 1 or x > 5

Question 13

What is the coefficient of x3x^3 in the Maclaurin series for e2xe^{2x}?

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 14

Find the exact sum of ∑n=1∞(−1)n+1n 2n\displaystyle\sum_{n=1}^{\infty} \frac{(-1)^{n+1}}{n\, 2^n}.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.

Question 15

Use series to find lim⁡x→0x−arctan⁡xx3\displaystyle\lim_{x\to 0} \frac{x - \arctan x}{x^3}.

Enter a number. Fractions like 3/4 and sqrt(2) are OK.