A mistake includes but is not limited to a false statement; a statement that is not a logic consequence of its proceeding statement; a statement that is not usefull for or related to the final results. Prove lim,-2 3x2 – - x = 14. Proof for e > 0, we need 3x2 – x – 14| < e. This is |(x +2)(3.x – 7)|< e SO |æ + 2| < |3x – 7| |3x| + 7 Therefore, we just need to pick 8 = $, then when |x + 2| < 8 = , we have |(x + 2)(3x – 7)|< e whch shows the limit=14.

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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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### Understanding Limits: Proving a Limit Example

#### Introduction
In calculus, understanding and proving limits are fundamental skills. Here, we'll go through the process of proving a specific limit: 

**Prove** 
\[
\lim_{x \to -2} (3x^2 - x) = 14.
\]

#### Proof
For any \(\epsilon > 0\), we need to show that:

\[
|3x^2 - x - 14| < \epsilon.
\]

This equation can be rewritten as:

\[
|(x + 2)(3x - 7)| < \epsilon.
\]

#### Steps to Prove the Limit
1. **Inequality Manipulation:**

   We need:

   \[
   |x + 2| < \frac{\epsilon}{|3x - 7|} < \frac{\epsilon}{|3x| + 7} < \frac{\epsilon}{7}.
   \]

   This leads us to pick our \(\delta\).

2. **Choosing \(\delta\):**

   We choose \(\delta = \frac{\epsilon}{7}\).

3. **Final Step:**

   Whenever \(|x + 2| < \delta = \frac{\epsilon}{7}\), we achieve:

   \[
   |(x + 2)(3x - 7)| < \epsilon.
   \]

Thus, this confirms that the limit is indeed \(14\).

### Conclusion
Through this process, we demonstrated how to approach and prove the limit using the \(\epsilon\)-\(\delta\) definition. This structured method ensures precise understanding and accuracy in limit evaluations.
Transcribed Image Text:### Understanding Limits: Proving a Limit Example #### Introduction In calculus, understanding and proving limits are fundamental skills. Here, we'll go through the process of proving a specific limit: **Prove** \[ \lim_{x \to -2} (3x^2 - x) = 14. \] #### Proof For any \(\epsilon > 0\), we need to show that: \[ |3x^2 - x - 14| < \epsilon. \] This equation can be rewritten as: \[ |(x + 2)(3x - 7)| < \epsilon. \] #### Steps to Prove the Limit 1. **Inequality Manipulation:** We need: \[ |x + 2| < \frac{\epsilon}{|3x - 7|} < \frac{\epsilon}{|3x| + 7} < \frac{\epsilon}{7}. \] This leads us to pick our \(\delta\). 2. **Choosing \(\delta\):** We choose \(\delta = \frac{\epsilon}{7}\). 3. **Final Step:** Whenever \(|x + 2| < \delta = \frac{\epsilon}{7}\), we achieve: \[ |(x + 2)(3x - 7)| < \epsilon. \] Thus, this confirms that the limit is indeed \(14\). ### Conclusion Through this process, we demonstrated how to approach and prove the limit using the \(\epsilon\)-\(\delta\) definition. This structured method ensures precise understanding and accuracy in limit evaluations.
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