(a) Prove that, for each k E N, b - Ck = ak and b+ Ck = |ak]. (b) Prove that, if ak converges conditionally, then b and C both diverge.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
icon
Related questions
Topic Video
Question
### Problem Description

**Sequence Definitions:**

Let \(\{a_k\}\) be a sequence of real numbers and sequences \(\{b_k\}\) and \(\{c_k\}\) be defined by the following rules:

\[
b_k = 
\begin{cases} 
a_k & \text{if } a_k > 0 \\
0 & \text{if } a_k \leq 0 
\end{cases}
\quad \text{and} \quad
c_k = 
\begin{cases} 
-a_k & \text{if } a_k < 0 \\
0 & \text{if } a_k \geq 0 
\end{cases}
\]

**Statements to Prove:**

(a) Prove that, for each \( k \in \mathbb{N} \), \(b_k - c_k = a_k\) and \(b_k + c_k = |a_k|\).

(b) Prove that, if \(\sum a_k\) converges conditionally, then \(\sum b_k\) and \(\sum c_k\) both diverge.

### Explanation of Problem Components

**Sequences \(\{a_k\}\), \(\{b_k\}\), \(\{c_k\}\):**
- The sequence \(\{a_k\}\) is any sequence of real numbers.
- The sequence \(\{b_k\}\) includes only the positive values from \(\{a_k\}\) and sets everything else to 0.
- The sequence \(\{c_k\}\) includes the negative values from \(\{a_k\}\) as positive (since \(c_k = -a_k\)) and sets everything else to 0.

### Detailed Steps

**Part (a):**

1. **To show \(b_k - c_k = a_k\):**
   - If \(a_k > 0\), then
     - \(b_k = a_k\),
     - \(c_k = 0\),
     - Thus, \(b_k - c_k = a_k - 0 = a_k\).
   - If \(a_k \leq 0\), then
     - \(b_k = 0\),
     - \(c_k = -a_k\) (note: \(-a_k\) is
Transcribed Image Text:### Problem Description **Sequence Definitions:** Let \(\{a_k\}\) be a sequence of real numbers and sequences \(\{b_k\}\) and \(\{c_k\}\) be defined by the following rules: \[ b_k = \begin{cases} a_k & \text{if } a_k > 0 \\ 0 & \text{if } a_k \leq 0 \end{cases} \quad \text{and} \quad c_k = \begin{cases} -a_k & \text{if } a_k < 0 \\ 0 & \text{if } a_k \geq 0 \end{cases} \] **Statements to Prove:** (a) Prove that, for each \( k \in \mathbb{N} \), \(b_k - c_k = a_k\) and \(b_k + c_k = |a_k|\). (b) Prove that, if \(\sum a_k\) converges conditionally, then \(\sum b_k\) and \(\sum c_k\) both diverge. ### Explanation of Problem Components **Sequences \(\{a_k\}\), \(\{b_k\}\), \(\{c_k\}\):** - The sequence \(\{a_k\}\) is any sequence of real numbers. - The sequence \(\{b_k\}\) includes only the positive values from \(\{a_k\}\) and sets everything else to 0. - The sequence \(\{c_k\}\) includes the negative values from \(\{a_k\}\) as positive (since \(c_k = -a_k\)) and sets everything else to 0. ### Detailed Steps **Part (a):** 1. **To show \(b_k - c_k = a_k\):** - If \(a_k > 0\), then - \(b_k = a_k\), - \(c_k = 0\), - Thus, \(b_k - c_k = a_k - 0 = a_k\). - If \(a_k \leq 0\), then - \(b_k = 0\), - \(c_k = -a_k\) (note: \(-a_k\) is
Expert Solution
steps

Step by step

Solved in 4 steps with 4 images

Blurred answer
Knowledge Booster
Sequence
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, advanced-math and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Advanced Engineering Mathematics
Advanced Engineering Mathematics
Advanced Math
ISBN:
9780470458365
Author:
Erwin Kreyszig
Publisher:
Wiley, John & Sons, Incorporated
Numerical Methods for Engineers
Numerical Methods for Engineers
Advanced Math
ISBN:
9780073397924
Author:
Steven C. Chapra Dr., Raymond P. Canale
Publisher:
McGraw-Hill Education
Introductory Mathematics for Engineering Applicat…
Introductory Mathematics for Engineering Applicat…
Advanced Math
ISBN:
9781118141809
Author:
Nathan Klingbeil
Publisher:
WILEY
Mathematics For Machine Technology
Mathematics For Machine Technology
Advanced Math
ISBN:
9781337798310
Author:
Peterson, John.
Publisher:
Cengage Learning,
Basic Technical Mathematics
Basic Technical Mathematics
Advanced Math
ISBN:
9780134437705
Author:
Washington
Publisher:
PEARSON
Topology
Topology
Advanced Math
ISBN:
9780134689517
Author:
Munkres, James R.
Publisher:
Pearson,