1. Suppose f is continuous on R and f satisfies f(x) + f(2x) = 0 for all x E R. Prove that f = 0 on R.

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Author:Erwin Kreyszig
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### Mathematical Analysis Problem:

1. **Problem Statement**:
   Suppose \( f \) is continuous on \(\mathbb{R}\) and \( f \) satisfies 
   \[
   f(x) + f(2x) = 0
   \]
   for all \( x \in \mathbb{R} \). Prove that \( f = 0 \) on \(\mathbb{R}\).

### Solution:
To solve this problem, we need to utilize the given functional equation along with the property of continuity of \( f \). Here's a step-by-step approach to derive the conclusion.

1. **Given Information**:
   - \( f \) is continuous on \(\mathbb{R}\).
   - \( f(x) + f(2x) = 0 \) for all \( x \in \mathbb{R} \).

2. **Initial Setup**:
   - Evaluate the functional equation for specific values and investigate how \( f \) behaves.
   - Particularly, choosing \( x = 0 \) may reveal some initial insights.

3. **Evaluation at Specific Points**:
   - Substitute \( x = 0 \) into the equation:
     \[
     f(0) + f(0) = 0 \implies 2f(0) = 0 \implies f(0) = 0
     \]
   - This provides us with the initial value: \( f(0) = 0 \).

4. **Extend to Other Points**:
   - Substitute \( x = \frac{1}{2} \):
     \[
     f\left(\frac{1}{2}\right) + f(1) = 0 \implies f(1) = -f\left(\frac{1}{2}\right)
     \]
   - Similarly, substituting \( x = 1 \):
     \[
     f(1) + f(2) = 0 \implies f(2) = -f(1) = f\left(\frac{1}{2}\right)
     \]
   - For \( x = 2 \):
     \[
     f(2) + f(4) = 0 \implies f(4) = -f(2) = -f\left(\frac{1}{2}\right)
     \]
   - Sub
Transcribed Image Text:### Mathematical Analysis Problem: 1. **Problem Statement**: Suppose \( f \) is continuous on \(\mathbb{R}\) and \( f \) satisfies \[ f(x) + f(2x) = 0 \] for all \( x \in \mathbb{R} \). Prove that \( f = 0 \) on \(\mathbb{R}\). ### Solution: To solve this problem, we need to utilize the given functional equation along with the property of continuity of \( f \). Here's a step-by-step approach to derive the conclusion. 1. **Given Information**: - \( f \) is continuous on \(\mathbb{R}\). - \( f(x) + f(2x) = 0 \) for all \( x \in \mathbb{R} \). 2. **Initial Setup**: - Evaluate the functional equation for specific values and investigate how \( f \) behaves. - Particularly, choosing \( x = 0 \) may reveal some initial insights. 3. **Evaluation at Specific Points**: - Substitute \( x = 0 \) into the equation: \[ f(0) + f(0) = 0 \implies 2f(0) = 0 \implies f(0) = 0 \] - This provides us with the initial value: \( f(0) = 0 \). 4. **Extend to Other Points**: - Substitute \( x = \frac{1}{2} \): \[ f\left(\frac{1}{2}\right) + f(1) = 0 \implies f(1) = -f\left(\frac{1}{2}\right) \] - Similarly, substituting \( x = 1 \): \[ f(1) + f(2) = 0 \implies f(2) = -f(1) = f\left(\frac{1}{2}\right) \] - For \( x = 2 \): \[ f(2) + f(4) = 0 \implies f(4) = -f(2) = -f\left(\frac{1}{2}\right) \] - Sub
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