VE -1 lim エ→1 エー1 = 1/2

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#121 part b
**Mathematics - Limits and Continuity**

---

**Problem 120: Evaluating Limits using Definitions**

- **Task**: Use the definition of a limit to verify that 

\[
\lim_{{x \to a}} \frac{{x^2 - a^2}}{{x - a}} = 2a.
\]

---

**Problem 121: Verifying Limits**

(a) 

\[
\lim_{{x \to 1}} \frac{{x^3 - 1}}{{x - 1}} = 3
\]

**Hint**:

\[
\left| \frac{{x^3 - 1}}{{x - 1}} - 3 \right| = \left| x^2 + x + 1 - 3 \right| 
\]

\[
\leq \left| x^2 - 1 \right| + \left| x - 1 \right| 
\]

\[
= \left| (x - 1)(x + 1) \right| + \left| x - 1 \right| 
\]

\[
= \left| (x - 1) \right| \cdot \left( \left| x + 1 \right| + 1 \right) 
\]

\[
\leq \left| x - 1 \right|^2 + 3 \left| x - 1 \right|.
\]

(b) 

\[
\lim_{{x \to 1}} \frac{{\sqrt{x} - 1}}{{x - 1}} = \frac{1}{2}
\]

---

**Continuity: What It Isn’t and What It Is**

**Hint**:

\[
\left| \frac{{\sqrt{x} - 1}}{{x - 1}} - \frac{1}{2} \right| 
\]

\[
= \left| \frac{1}{{\sqrt{x} + 1}} - \frac{1}{2} \right| 
\]

\[
= \frac{2 - (\sqrt{x} + 1)}{2(\sqrt{x} + 1)} 
\]

\[
= \frac{1 - x}{2(1 + \sqrt{x})^2}
\]

\[
\leq \frac{1}{2} \left| x
Transcribed Image Text:**Mathematics - Limits and Continuity** --- **Problem 120: Evaluating Limits using Definitions** - **Task**: Use the definition of a limit to verify that \[ \lim_{{x \to a}} \frac{{x^2 - a^2}}{{x - a}} = 2a. \] --- **Problem 121: Verifying Limits** (a) \[ \lim_{{x \to 1}} \frac{{x^3 - 1}}{{x - 1}} = 3 \] **Hint**: \[ \left| \frac{{x^3 - 1}}{{x - 1}} - 3 \right| = \left| x^2 + x + 1 - 3 \right| \] \[ \leq \left| x^2 - 1 \right| + \left| x - 1 \right| \] \[ = \left| (x - 1)(x + 1) \right| + \left| x - 1 \right| \] \[ = \left| (x - 1) \right| \cdot \left( \left| x + 1 \right| + 1 \right) \] \[ \leq \left| x - 1 \right|^2 + 3 \left| x - 1 \right|. \] (b) \[ \lim_{{x \to 1}} \frac{{\sqrt{x} - 1}}{{x - 1}} = \frac{1}{2} \] --- **Continuity: What It Isn’t and What It Is** **Hint**: \[ \left| \frac{{\sqrt{x} - 1}}{{x - 1}} - \frac{1}{2} \right| \] \[ = \left| \frac{1}{{\sqrt{x} + 1}} - \frac{1}{2} \right| \] \[ = \frac{2 - (\sqrt{x} + 1)}{2(\sqrt{x} + 1)} \] \[ = \frac{1 - x}{2(1 + \sqrt{x})^2} \] \[ \leq \frac{1}{2} \left| x
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