5. Suppose {pn}=1 is a Cauchy sequence in a metric space, , and some subsequence {pn} converges to a point, p E X. Prove the full sequence, {pn}n=1 converges to p U 00 3n

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Question 5
# Convergence and Cauchy Sequences in Real Analysis

**1. Use the definition of a convergent sequence to show that \( \left\{ 7 - \frac{4}{n} \right\}_{n=1}^{\infty} \) converges to 7**  
Where \( \left\{ 7 - \frac{4}{n} \right\}_{n=1}^{\infty} \) is considered to be a sequence in \( \mathbb{R} \) with the usual metric \( d_{\mathbb{R}}(x,y) = |x - y| \).

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

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

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

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