Limit Evaluation 666Adb
1. **State the problem:**
Find the limit of the function $$f(x) = \frac{x^2 - 3x}{x^2 - 9}$$ as $$x$$ approaches 3 and -3 by evaluating the function at values close to these points.
2. **Recall the formula and important rules:**
The limit $$\lim_{x \to a} f(x)$$ is the value that $$f(x)$$ approaches as $$x$$ gets arbitrarily close to $$a$$.
3. **Simplify the function:**
Factor numerator and denominator:
$$x^2 - 3x = x(x - 3)$$
$$x^2 - 9 = (x - 3)(x + 3)$$
So,
$$f(x) = \frac{x(x - 3)}{(x - 3)(x + 3)}$$
For $$x \neq 3$$, cancel $$x - 3$$:
$$f(x) = \frac{x}{x + 3}$$
4. **Evaluate the limit as $$x \to 3$$:**
Substitute $$x = 3$$ into simplified function:
$$f(3) = \frac{3}{3 + 3} = \frac{3}{6} = 0.5$$
5. **Evaluate the limit as $$x \to -3$$:**
Simplified function is $$f(x) = \frac{x}{x + 3}$$, but at $$x = -3$$ denominator is zero, so check values near -3:
- For $$x$$ approaching -3 from the right (e.g., -2.9999), denominator $$x + 3$$ is positive but very small, numerator $$x$$ is negative, so $$f(x)$$ tends to $$-\infty$$.
- For $$x$$ approaching -3 from the left (e.g., -3.0001), denominator $$x + 3$$ is negative and very small, numerator $$x$$ is negative, so $$f(x)$$ tends to $$+\infty$$.
6. **Conclusion:**
- $$\lim_{x \to 3} f(x) = 0.5$$
- $$\lim_{x \to -3} f(x)$$ does not exist because the left and right limits are not equal (one tends to $$+\infty$$, the other to $$-\infty$$).
7. **Verification by numerical substitution:**
- At $$x=3.1$$, $$f(3.1) \approx \frac{3.1}{6.1} = 0.508197$$
- At $$x=2.9$$, $$f(2.9) \approx \frac{2.9}{5.9} = 0.491525$$
Values approach 0.5 as $$x \to 3$$.
- At $$x=-2.9999$$, $$f(-2.9999) \approx \frac{-2.9999}{0.0001} = -29999$$ (large negative)
- At $$x=-3.0001$$, $$f(-3.0001) \approx \frac{-3.0001}{-0.0001} = 30001$$ (large positive)
This confirms the limit behavior at $$x = -3$$.
**Final answers:**
$$\lim_{x \to 3} \frac{x^2 - 3x}{x^2 - 9} = 0.5$$
$$\lim_{x \to -3} \frac{x^2 - 3x}{x^2 - 9} \text{ does not exist}$$