2. Prove the limit ratio test (Corollary 3.8 in the notes): Suppose {an} is a sequence of nonzero real numbers and r(n) = |"n+1|. Suppose further that lim,+ r(n) = L. Show that (i) If L < 1, the series an converges absolutely. (ii) If L > 1, the series an diverges. Hint. This is a Corollary to the ratio test (Theorem 3.6 in the notes), so you should be using the ratio test in your proof. n→∞

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Chapter2: Second-order Linear Odes
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2. Prove the limit ratio test (Corollary 3.8 in the notes): Suppose \(\{a_n\}\) is a sequence of nonzero real numbers and

\[
r(n) = \left| \frac{a_{n+1}}{a_n} \right|.
\]

Suppose further that \(\lim_{n \to \infty} r(n) = L\). Show that

(i) If \(L < 1\), the series \(\sum a_n\) converges absolutely.

(ii) If \(L > 1\), the series \(\sum a_n\) diverges.

*Hint*: This is a Corollary to the ratio test (Theorem 3.6 in the notes), so you should be using the ratio test in your proof.
Transcribed Image Text:2. Prove the limit ratio test (Corollary 3.8 in the notes): Suppose \(\{a_n\}\) is a sequence of nonzero real numbers and \[ r(n) = \left| \frac{a_{n+1}}{a_n} \right|. \] Suppose further that \(\lim_{n \to \infty} r(n) = L\). Show that (i) If \(L < 1\), the series \(\sum a_n\) converges absolutely. (ii) If \(L > 1\), the series \(\sum a_n\) diverges. *Hint*: This is a Corollary to the ratio test (Theorem 3.6 in the notes), so you should be using the ratio test in your proof.
**Theorem 3.6 (Ratio Test).** Let \( a_n \) be a sequence of nonzero real numbers and let

\[
r(n) = \left| \frac{a_{n+1}}{a_n} \right|.
\]

(i) If there exists \( c < 1 \) so that \( r(n) \leq c \) for all \( n \), then the series \( \sum a_n \) converges absolutely.

(ii) If \( r(n) \geq 1 \) for all \( n \), then the series \( \sum a_n \) diverges.
Transcribed Image Text:**Theorem 3.6 (Ratio Test).** Let \( a_n \) be a sequence of nonzero real numbers and let \[ r(n) = \left| \frac{a_{n+1}}{a_n} \right|. \] (i) If there exists \( c < 1 \) so that \( r(n) \leq c \) for all \( n \), then the series \( \sum a_n \) converges absolutely. (ii) If \( r(n) \geq 1 \) for all \( n \), then the series \( \sum a_n \) diverges.
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