redthumb edited alternating series.tex  over 9 years ago

Commit id: 05652fa418233f20f3e27a5f3d0130a5f48a170c

deletions | additions      

       

Ratio Test:  \begin{align}  L\hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left|b(n\:+\: 1)\hspace{1em}\div\hspace{1em}b(n)\right| \tag{15}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{(n\:+\:1\:+\:1)}{(n\:+\:1)^3}\hspace{1em}\div\hspace{1em}\frac{(n\:+\:1)}{n^3}\right| \tag{16}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{(n\:+\:2)}{(n\:+\:1)^3}\hspace{1em}\div\hspace{1em}\frac{(n\:+\:1)}{n^3}\right| \tag{17}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{(n\:+\:2)}{(n\:+\:1)^3}\hspace{1em}\div\hspace{1em}\frac{(n\:+\:1)}{n^3}\right| \tag{18}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{(n\:+\:2)}{(n\:+\:1)^3}\hspace{1em}\cdot\hspace{1em}\frac{n^3}{(n\:+\:1)}\right| \tag{19}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^3(n\:+\:2)}{(n\:+\:1)(n\:+\:1)^3}\right| \tag{20}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^3(n\:+\:2)}{(n\:+\:1)(n\:+\:1)(n\:+\:1)(n\:+\:1)}\right| \tag{21}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^3(n\:+\:2)}{(n^2\:+\:2n\:+\:1)(n\:+\:1)(n\:+\:1)}\right| \tag{22}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^3(n\:+\:2)}{(n^3\:+\:3n^2\:+\:3n\:+\:1)(n\:+\:1)}\right| \tag{23}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^3(n\:+\:2)}{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1)}\right| \tag{24}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{n^4\left(\frac{n}{n}\:+\:\frac{2}{n}\right)}{n^4\left(\frac{n^4}{n^4}\:+\:\frac{4n^3}{n^4}\:+\:\frac{6n^2}{n^4}\:+\:\frac{4n}{n^4}\:+\:\frac{1}{n^4}\right)}\right| \tag{25}\\[1em] \\[1em]  &=\hspace{1em}\lim_{n\to\infty} \left|\frac{\left(1\:+\:\frac{2}{n}\right)}{\left(1\:+\:\frac{4}{n}\:+\:\frac{6}{n^2}\:+\:\frac{4}{n^3}\:+\:\frac{1}{n^4}\right)}\right| \tag{26}\\[1em] \\[1em]  &=\hspace{1em} \left|\frac{\left(1\:+\:\frac{2}{\infty}\right)}{\left(1\:+\:\frac{4}{\infty}\:+\:\frac{6}{\infty}\:+\:\frac{4}{\infty}\:+\:\frac{1}{\infty}\right)}\right| \tag{27}\\[1em] \\[1em]  &=\hspace{1em} \left|\frac{\left(1\:+\:0\right)}{\left(1\:+\:0\:+\:0\:+\:0\:+\:0\right)}\right| \tag{28}\\[1em] \\[1em]  &=\hspace{1em} \left|\frac{1}{1}\right| \tag{28}\\[1em] \\[1em]  L\hspace{1em}&=\hspace{1em} [1] \tag{29}\\[1em] \\[1em]  \end{align}  Ratio Test Condidtions: 

Raabe's Test:  \begin{align}  L\hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(b(n)\hspace{1em}\div\hspace{1em}b(n\:+\:1)\right)\hspace{1em}-\hspace{1em}1\right] \tag{30}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n\:+\:1)}{n^3}\hspace{1em}\div\hspace{1em}\frac{(n\:+\:1\:+\:1)}{(n\:+\:1)^3}\right)\hspace{1em}-\hspace{1em}1\right] \tag{31}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n\:+\:1)}{n^3}\hspace{1em}\div\hspace{1em}\frac{(n\:+\:2)}{(n\:+\:1)^3}\right)\hspace{1em}-\hspace{1em}1\right] \tag{32}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n\:+\:2)}{n^3}\hspace{1em}\cdot\hspace{1em}\frac{(n\:+\:1)^3}{(n\:+\:1)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{33}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n\:+\:1)(n\:+\:1)^3}{n^3(n\:+\:2)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{34}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n\:+\:1)(n\:+\:1)(n\:+\:1)(n\:+\:1)}{n^3(n\:+\:2)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{35}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^2\:+\:2n\:+\:1)(n\:+\:1)(n\:+\:1)}{n^3(n\:+\:2)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{36}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^3\:+\:3n^2\:+\:3n\:+\:1)(n\:+\:1)}{n^3(n\:+\:2)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{37}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1)}{n^3(n\:+\:2)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{38}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1)}{(n^4\:+\:2n^3)}\right)\hspace{1em}-\hspace{1em}1\right] \tag{39}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1)}{(n^4\:+\:2n^3)}\right)\hspace{1em}-\hspace{1em}\frac{(n^4\:+\:2n^3)}{(n^4\:+\:2n^3)}\right] \tag{40}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1)\hspace{1em}-\hspace{1em}(n^4\:+\:2n^3)}{(n^4\:+\:2n^3)}\right)\right] \tag{41}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(n^4\:+\:4n^3\:+\:6n^2\:+\:4n\:+\:1\:-\:n^4\:-\:2n^3)}{(n^4\:+\:2n^3)}\right)\right] \tag{42}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[n\cdot\left(\frac{(2n^3\:+\:6n^2\:+\:4n\:+\:1)}{(n^4\:+\:2n^3)}\right)\right] \tag{43}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[\frac{n\cdot(2n^3\:+\:6n^2\:+\:4n\:+\:1)}{(n^4\:+\:2n^3)}\right] \tag{44}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[\frac{n\cdot n^3\cdot\left(\frac{2n^3}{n^3}\:+\:\frac{6n^2}{n^3}\:+\:\frac{4n}{n^3}\:+\:\frac{2}{n^3}\right)}{n^4\cdot\left(\frac{n^4}{n^4}\:+\:\frac{n^3}{n^4}\right)}\right] \tag{45}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em}\lim_{n\to\infty} \left[\frac{\left(2\:+\:\frac{6}{n}\:+\:\frac{4}{n^2}\:+\:\frac{1}{n^3}\right)}{\left(1\:+\:\frac{1}{n}\right)}\right] \tag{46}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em} \left[\frac{\left(2\:+\:\frac{6}{\infty}\:+\:\frac{4}{\infty}\:+\:\frac{1}{\infty}\right)}{\left(1\:+\:\frac{1}{\infty}\right)}\right] \tag{47}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em} \left[\frac{\left(2\:+\:0\:+\:0\:+\:0\right)}{\left(1\:+\:0\right)}\right] \tag{48}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em} \left[\frac{\left(2\right)}{\left(1\right)}\right] \tag{49}\\[1em] \\[1em]  \hspace{1em}&=\hspace{1em} \left[2\right] \tag{50}\\[1em] \\[1em]  \end{align}  Raabe's Conditions: