The following proposition is clearly wrong. Provide a counterexample, and explain what is wrong with the proof. Proposition. For all n ≥ 1, for all a₁,..., an € R, we have a₁ = A2 = ... = an. Proof. We will prove by induction on n. Base Case: For n = 1, let a₁ € R. Then a₁ = a₁. 1 Inductive Step: Assume that for all a₁,... an ER, we have a₁ = = an. We will prove that for all a₁,..., an+1 € R, we have an+1. a2 = a₁ Let a₁,..., an+1 be in R. Observe that • Since a₁,... an are n real numbers, by inductive hypothesis, we know that a₁. = An. • Since a2,...an+1 are n real numbers, by inductive hypothesis, we know that a2 = ··· = An = An+1. (Note that the inductive hypothesis is a for-all statement, so we can apply it to any n real numbers.

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The following proposition is clearly wrong. Provide a counterexample, and explain what is wrong with the proof.

**Proposition.** For all \( n \geq 1 \), for all \( a_1, \ldots, a_n \in \mathbb{R} \), we have \( a_1 = a_2 = \cdots = a_n \).

**Proof.** We will prove by induction on \( n \).

**Base Case:** For \( n = 1 \), let \( a_1 \in \mathbb{R} \). Then \( a_1 = a_1 \).

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**Inductive Step:** Assume that for all \( a_1, \ldots, a_n \in \mathbb{R} \), we have \( a_1 = a_2 = \cdots = a_n \). We will prove that for all \( a_1, \ldots, a_{n+1} \in \mathbb{R} \), we have \( a_1 = \cdots = a_{n+1} \).

Let \( a_1, \ldots, a_{n+1} \) be in \( \mathbb{R} \). Observe that:

- Since \( a_1, \ldots, a_n \) are \( n \) real numbers, by inductive hypothesis, we know that \( a_1 = \cdots = a_n \).
- Since \( a_2, \ldots, a_{n+1} \) are \( n \) real numbers, by inductive hypothesis, we know that \( a_2 = \cdots = a_n = a_{n+1} \). (Note that the inductive hypothesis is a for-all statement, so we can apply it to any \( n \) real numbers.)

Therefore, we have \( a_1 = \cdots = a_n \), and \( a_n = a_{n+1} \), so \( a_1 = \cdots = a_n = a_{n+1} \).

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This proof is incorrect. Can you find the error and provide a counterexample?
Transcribed Image Text:The following proposition is clearly wrong. Provide a counterexample, and explain what is wrong with the proof. **Proposition.** For all \( n \geq 1 \), for all \( a_1, \ldots, a_n \in \mathbb{R} \), we have \( a_1 = a_2 = \cdots = a_n \). **Proof.** We will prove by induction on \( n \). **Base Case:** For \( n = 1 \), let \( a_1 \in \mathbb{R} \). Then \( a_1 = a_1 \). --- **Inductive Step:** Assume that for all \( a_1, \ldots, a_n \in \mathbb{R} \), we have \( a_1 = a_2 = \cdots = a_n \). We will prove that for all \( a_1, \ldots, a_{n+1} \in \mathbb{R} \), we have \( a_1 = \cdots = a_{n+1} \). Let \( a_1, \ldots, a_{n+1} \) be in \( \mathbb{R} \). Observe that: - Since \( a_1, \ldots, a_n \) are \( n \) real numbers, by inductive hypothesis, we know that \( a_1 = \cdots = a_n \). - Since \( a_2, \ldots, a_{n+1} \) are \( n \) real numbers, by inductive hypothesis, we know that \( a_2 = \cdots = a_n = a_{n+1} \). (Note that the inductive hypothesis is a for-all statement, so we can apply it to any \( n \) real numbers.) Therefore, we have \( a_1 = \cdots = a_n \), and \( a_n = a_{n+1} \), so \( a_1 = \cdots = a_n = a_{n+1} \). --- This proof is incorrect. Can you find the error and provide a counterexample?
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