What is wrong with the following “proof" of the "fact" that n+3 = n+7 for all values of n (besides of course that the thing it is claiming to prove is false)? Proof. Let P(n) be the statement that n + 3 = n + 7. We will prove that P(n) is true for all n e N. Assume, for induction that P(k) is true. That is, k + 3 = k + 7. We must show that P(k + 1) is true. Now since k +3 = k + 7, add 1 to both sides. This gives k + 3 +1 = k + 7 + 1. %3D

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Chapter2: Second-order Linear Odes
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**Title: Flawed Proof of a Mathematical Statement**

**Description:**

In this example, we examine a flawed proof regarding the statement that \( n + 3 = n + 7 \) for all values of \( n \). Apart from the obvious fact that the claim itself is false, let's explore what's wrong with the proof provided.

**Proof Analysis:**

1. **Statement Definition:**
   - Let \( P(n) \) be the proposition that \( n + 3 = n + 7 \).

2. **Proof by Induction:**
   - We aim to prove that \( P(n) \) holds for all \( n \in \mathbb{N} \).

3. **Base Case:**
   - Assume, for induction, that \( P(k) \) is true.
   - That is, assume \( k + 3 = k + 7 \).

4. **Inductive Step:**
   - We must show that \( P(k + 1) \) holds true.
   - Adding 1 to both sides of \( k + 3 = k + 7 \) gives: 
     \[
     k + 3 + 1 = k + 7 + 1 
     \]
   - Simplifies to: 
     \[
     (k + 1) + 3 = (k + 1) + 7
     \]
   - This is equivalent to the statement that \( P(k + 1) \) holds true.

5. **Conclusion:**
   - According to this reasoning, by the principle of mathematical induction, \( P(n) \) is purportedly true for all \( n \in \mathbb{N} \).

**QED Error:**
- The error lies in the incorrect assumption during the inductive step where it is assumed \( k + 3 = k + 7 \) is true for any integer \( k \). This foundational assumption is false, and thus invalidates the entire proof.
Transcribed Image Text:**Title: Flawed Proof of a Mathematical Statement** **Description:** In this example, we examine a flawed proof regarding the statement that \( n + 3 = n + 7 \) for all values of \( n \). Apart from the obvious fact that the claim itself is false, let's explore what's wrong with the proof provided. **Proof Analysis:** 1. **Statement Definition:** - Let \( P(n) \) be the proposition that \( n + 3 = n + 7 \). 2. **Proof by Induction:** - We aim to prove that \( P(n) \) holds for all \( n \in \mathbb{N} \). 3. **Base Case:** - Assume, for induction, that \( P(k) \) is true. - That is, assume \( k + 3 = k + 7 \). 4. **Inductive Step:** - We must show that \( P(k + 1) \) holds true. - Adding 1 to both sides of \( k + 3 = k + 7 \) gives: \[ k + 3 + 1 = k + 7 + 1 \] - Simplifies to: \[ (k + 1) + 3 = (k + 1) + 7 \] - This is equivalent to the statement that \( P(k + 1) \) holds true. 5. **Conclusion:** - According to this reasoning, by the principle of mathematical induction, \( P(n) \) is purportedly true for all \( n \in \mathbb{N} \). **QED Error:** - The error lies in the incorrect assumption during the inductive step where it is assumed \( k + 3 = k + 7 \) is true for any integer \( k \). This foundational assumption is false, and thus invalidates the entire proof.
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