Calculus 2 : Series in Calculus

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #71 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{n7^n}{5^{2n}}\newline note: \hspace f(n) = \frac{n7^n}{5^{2n}}\)

Possible Answers:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{25}{7}\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{7^{n+1}\left(n+1\right)}{5^{2\left(n+1\right)}}}{\frac{7^nn}{5^{2n}}} = \frac{5^{2n}\cdot \:7^{n+1}\left(n+1\right)}{5^{2\left(n+1\right)}\cdot \:7^nn} = \frac{7\left(n+1\right)}{25n}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{7\left(n+1\right)}{25n} = \frac{7}{25}\)

Example Question #72 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{7^n}{n5^{2n}}\newline note: \hspace f(n) = \frac{7^n}{n5^{2n}}\)

Possible Answers:

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{25}{7}\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{7^{n+1}}{5^{2\left(n+1\right)}\left(n+1\right)}}{\frac{7^n}{5^{2n}n}}= \frac{5^{2n}\cdot \:7^{n+1}n}{5^{2\left(n+1\right)}\cdot \:7^n\left(n+1\right)} = \frac{7n}{25\left(n+1\right)}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{7n}{25\left(n+1\right)} = \frac{7}{25}\)

Example Question #73 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{n4^n}{3^{2n}}\newline note: \hspace f(n) = \frac{n4^n}{3^{2n}}\)

Possible Answers:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{4}{9}\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{9}{4}\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{4}{9}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{4^{n+1}\left(n+1\right)}{3^{2\left(n+1\right)}}}{\frac{4^nn}{3^{2n}}} = \frac{3^{2n}\cdot \:4^{n+1}\left(n+1\right)}{3^{2\left(n+1\right)}\cdot \:4^nn} = \frac{4\left(n+1\right)}{9n}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{4\left(n+1\right)}{9n} = \frac{4}{9}\)

Example Question #74 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{11^n}{n5^{3n}}\newline note: \hspace f(n) = \frac{11^n}{n5^{3n}}\)

Possible Answers:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{11}{125}\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{125}{11}\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{11}{125}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{11^{n+1}}{5^{3\left(n+1\right)}\left(n+1\right)}}{\frac{11^n}{5^{3n}n}} = \frac{5^{3n}\cdot \:11^{n+1}n}{5^{3\left(n+1\right)}\cdot \:11^n\left(n+1\right)} = \frac{11n}{125\left(n+1\right)}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{11n}{125\left(n+1\right)} = \frac{11}{125}\)

Example Question #75 : Series In Calculus

 

\(\displaystyle \\ \textup{Use the ratio test to find out if the following series is convergent:}\\ \sum_{n = 1}^{\infty} \frac{9^n}{4^{2n}}\newline note: \hspace f(n) = \frac{9^n}{4^{2n}}\)

Possible Answers:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{16}{9}\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{9}{16}\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{9}{16}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{9^{\left(n+1\right)}}{4^{2\left(n+1\right)}}}{\frac{9^n}{4^{2n}}} = \frac{4^{2n}\cdot \:9^{n+1}}{4^{2\left(n+1\right)}\cdot \:9^n} = \frac{9}{16}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{9}{16} = \frac{9}{16}\)

Example Question #76 : Series In Calculus

\(\displaystyle \\ \textup{Use the ratio test to find out if the following series is convergent:}\\ \sum_{n = 1}^{\infty} \frac{4^{2n}}{5\cdot \:6^{2n}}\newline note: \hspace f(n) = \frac{4^{2n}}{5\cdot \:6^{2n}}\)

Possible Answers:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 9\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{4}{9}\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{4}{9}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\left(\frac{2}{3}\right)^{2\left(n+1\right)}}{\left(\frac{2}{3}\right)^{2n}}=\left(\frac{2}{3}\right)^2=\frac{4}{9}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{4}{9} = \frac{4}{9}\)

Example Question #77 : Series In Calculus

\(\displaystyle \\ \textup{Use the ratio test to find out if the following series is convergent:}\\ \sum_{n = 1}^{\infty} \frac{7^n}{5^{2n}}\newline note: \hspace f(n) = \frac{7^n}{5^{2n}}\)

Possible Answers:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{25}{7}\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Correct answer:

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{7}{25}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{7^{n+1}}{5^{2\left(n+1\right)}}}{\frac{7^n}{5^{2n}}} = \frac{5^{2n}\cdot \:7^{n+1}}{5^{2\left(n+1\right)}\cdot \:7^n} = \frac{7}{25}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{7}{25} = \frac{7}{25}\)

 

 

Example Question #78 : Series In Calculus

\(\displaystyle \\ \textup{Use the ratio test to find out if the following series is convergent:}\\ \sum_{n = 1}^{\infty} \frac{10^n}{3^{2n}}\newline note: \hspace f(n) = \frac{10^n}{3^{2n}}\)

Possible Answers:

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{1}{3}\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{10}{9}\)

Correct answer:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{10}{9}\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline \textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

 

\(\displaystyle \frac{\frac{10^{\left(n+1\right)}}{3^{2\left(n+1\right)}}}{\frac{10^n}{3^{2n}}} = \frac{3^{2n}\cdot \:10^{n+1}}{3^{2\left(n+1\right)}\cdot \:10^n} = \frac{10}{9}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{10}{9} = \frac{10}{9}\)

Example Question #79 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{50n!}{n^{4}ln(n)} \newline note: \hspace f(n) = \frac{50n!}{n^{4}ln(n)}\)

Possible Answers:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{1}{4}\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 4\)

Correct answer:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{\left(n+1\right)!}{\left(n+1\right)^4\ln \left(\left(n+1\right)\right)}}{\frac{n!}{n^4\ln \left(n\right)}} = \frac{(n+1)!n^4ln(n)}{n!(n+1)^4ln(n+1)} = \frac{n^4ln(n)}{(n+1)^3ln(n+1)}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{n^4ln(n)}{(n+1)^3ln(n+1)} = \infty\)

Example Question #80 : Series In Calculus

\(\displaystyle \textnormal{Use the ratio test to find out if the following series is convergent:} \newline\sum_{n = 1}^{\infty} \frac{70n!}{n^{8}ln(n)}\newline note: \hspace f(n) = \frac{70n!}{n^{8}ln(n)}\)

Possible Answers:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = \frac{1}{8}\)

\(\displaystyle Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 0\)

\(\displaystyle Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\)

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 8\)

Correct answer:

\(\displaystyle Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} \rightarrow \infty\)

Explanation:

\(\displaystyle \newline \textnormal{Determine the convergence of the series based on the limits.}\newline Convergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} < 1 \newline Divergent: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} > 1 \newline Inconclusive: \lim_{n\rightarrow \infty} \frac{f(n+1)}{f(n)} = 1\newline\textnormal{Solution:} \newline\textnormal{1. Ignore constants and simplify the equation (canceling out what you can)}\newline\textnormal{2. Once the equation is simplified, take} \lim_{n\rightarrow \infty}\)

\(\displaystyle \frac{\frac{\left(n+1\right)!}{\left(n+1\right)^8\ln \left(\left(n+1\right)\right)}}{\frac{n!}{n^8\ln \left(n\right)}} = \frac{(n+1)!n^8ln(n)}{n!(n+1)^8ln(n+1)} = \frac{n^8ln(n)}{(n+1)^7ln(n+1)}\)

\(\displaystyle \lim_{n\rightarrow \infty} \frac{n^8ln(n)}{(n+1)^7ln(n+1)} = \infty\)

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