Using Properties of Convergent Sequences

Use properties of convergent sequences to find \(\lim\limits_{n\rightarrow \infty }s_{n}.\)

  1. \(\{ s_{n}\} =\left\{ \dfrac{2}{n}+3\right\}\)
  2. \(\{ s_{n}\} =\left\{\dfrac{4}{n^{2}}\right\}\)
  3. \(\{ s_{n}\} =\left\{ \sqrt[3]{\dfrac{16n^{2}+3n}{2n^{2}}}\right\}\)

Solution
(a) \[ \begin{eqnarray*} \lim\limits_{n\rightarrow \infty}s_{n}&=&\lim\limits_{n\rightarrow \infty }\left( \dfrac{2}{n}+3\right)=\lim\limits_{n\rightarrow \infty }\dfrac{2}{n}+\lim\limits_{n\rightarrow\infty }3\\ &=&2\lim\limits_{n\rightarrow \infty }\dfrac{1}{n}+\lim\limits_{n\rightarrow \infty }3 \underset{\underset{\color{#0066A7}{\lim\limits_{n\rightarrow \infty}\dfrac{1}{n}=0;\,\,\lim\limits_{n\rightarrow\infty} 3=3}}{\color{#0066A7}{\uparrow}}}{=} 2\cdot 0+3=3\\ \end{eqnarray*} \]

(b) \[ \begin{eqnarray*} \lim\limits_{n\rightarrow \infty }s_{n}=\lim\limits_{n\rightarrow \infty }\dfrac{4}{n^{2}}=4\lim\limits_{n\rightarrow \infty }\dfrac{1}{n^{2}}=4\lim\limits_{n\rightarrow \infty }\dfrac{1}{n}\cdot \lim\limits_{n\rightarrow \infty }\dfrac{1}{n} \underset{\underset{\color{#0066A7}{\lim\limits_{n\rightarrow \infty }\dfrac{1}{n}=0}}{\color{#0066A7}{\uparrow}}}{=} 4\cdot 0\cdot 0=0\\ \hspace{-7pc} \end{eqnarray*} \]

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(c) \[ \begin{eqnarray*} \lim\limits_{n\rightarrow \infty}s_{n} &=&\lim\limits_{n\rightarrow \infty }\sqrt[3]{\dfrac{16n^{2}+3n}{2n^{2}}}=\sqrt[3]{\lim\limits_{n\rightarrow \infty }\left( \dfrac{16n^{2}+3n}{2n^{2}} \right) }=\sqrt[3]{\lim\limits_{n\rightarrow \infty }\left( 8+\dfrac{3}{2n}\right) }\\ &=&\sqrt[3]{\lim\limits_{n\rightarrow \infty }8+\lim\limits_{n\rightarrow \infty }\dfrac{ 3}{2n}} \underset{\underset{\color{#0066A7}{\lim\limits_{n\rightarrow \infty }8=8}}{\color{#0066A7}{\uparrow}}}{=} \sqrt[3]{8+\dfrac{3}{2}\lim\limits_{n\rightarrow \infty } \dfrac{1}{n}} \underset{\underset{\color{#0066A7}{\lim\limits_{n\rightarrow \infty }\dfrac{1}{n}=0}}{\color{#0066A7}{\uparrow}}}{=} \sqrt[3]{8+\dfrac{3}{2}\cdot 0}=\sqrt[3]{8}=2 \\ \end{eqnarray*} \]