8. 3n 6. (a) Prove is a decreasing sequence in R (G. 3n-1) n=1 00 3n (b) Is a convergent sequence in R with the usual metric dº(x,y) = |x – y| 3n-1) n=1 (c) Is {-(n²)}=, a convergent sequence in R with the usual metric ?

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Question 6
**Convergence and Cauchy Sequences**

**1. Use the definition of a convergent sequence to show \( \left\{ 7 - \frac{4}{n} \right\}^\infty_{n=1} \) converges to 7.**

The sequence \( \left\{ 7 - \frac{4}{n} \right\}^\infty_{n=1} \) is considered to be a sequence in \( \mathbb{R} \) with the usual metric \( d_\mathbb{R}(x, y) = |x - y| \).

**2. Let \( \{s_n\}^\infty_{n=1} \) be an unbounded sequence of negative numbers. Show \( \{s_n\}^\infty_{n=1} \) has a subsequence \( \{s_{n_k}\}^\infty_{k=1} \) such that \( \{s_{n_k}\}^\infty_{k=1} \) tends to minus infinity.**

**3. Let \( \{a_n\}^\infty_{n=1} \), \( \{b_n\}^\infty_{n=1} \), \( \{c_n\}^\infty_{n=1} \), and \( \{d_n\}^\infty_{n=1} \) be Cauchy sequences in \( \mathbb{R} \) with the usual metric. Show \( \{x_n\}^\infty_{n=1} \) where \( x_n = (a_n, b_n, c_n, d_n) \) is Cauchy in \( \mathbb{R}^4 \).

**4. Prove \( \left\{ \frac{8n - 5}{n} \right\}^\infty_{n=1} \) is a Cauchy sequence in \( \mathbb{R} \) with the usual metric \( d_\mathbb{R}(x, y) = |x - y| \).

**5. Suppose \( \{p_n\}^\infty_{n=1} \) is a Cauchy sequence in a metric space, and some subsequence \( \{p_{n_i}\}^\infty_{i
Transcribed Image Text:**Convergence and Cauchy Sequences** **1. Use the definition of a convergent sequence to show \( \left\{ 7 - \frac{4}{n} \right\}^\infty_{n=1} \) converges to 7.** The sequence \( \left\{ 7 - \frac{4}{n} \right\}^\infty_{n=1} \) is considered to be a sequence in \( \mathbb{R} \) with the usual metric \( d_\mathbb{R}(x, y) = |x - y| \). **2. Let \( \{s_n\}^\infty_{n=1} \) be an unbounded sequence of negative numbers. Show \( \{s_n\}^\infty_{n=1} \) has a subsequence \( \{s_{n_k}\}^\infty_{k=1} \) such that \( \{s_{n_k}\}^\infty_{k=1} \) tends to minus infinity.** **3. Let \( \{a_n\}^\infty_{n=1} \), \( \{b_n\}^\infty_{n=1} \), \( \{c_n\}^\infty_{n=1} \), and \( \{d_n\}^\infty_{n=1} \) be Cauchy sequences in \( \mathbb{R} \) with the usual metric. Show \( \{x_n\}^\infty_{n=1} \) where \( x_n = (a_n, b_n, c_n, d_n) \) is Cauchy in \( \mathbb{R}^4 \). **4. Prove \( \left\{ \frac{8n - 5}{n} \right\}^\infty_{n=1} \) is a Cauchy sequence in \( \mathbb{R} \) with the usual metric \( d_\mathbb{R}(x, y) = |x - y| \). **5. Suppose \( \{p_n\}^\infty_{n=1} \) is a Cauchy sequence in a metric space, and some subsequence \( \{p_{n_i}\}^\infty_{i
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