Limit Evaluation C961Ab
1. **State the problem:**
We want to estimate the limits:
(a) $$\lim_{x \to 3} \frac{x^2 - 3x}{x^2 - 9}$$
(b) $$\lim_{x \to -3} \frac{x^2 - 3x}{x^2 - 9}$$
by evaluating the function at values close to 3 and -3 respectively.
2. **Simplify the function:**
The function is $$f(x) = \frac{x^2 - 3x}{x^2 - 9}$$.
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 $$x - 3$$:
$$f(x) = \frac{x}{x + 3}$$
3. **Evaluate the function near the limits:**
(a) For $$x \to 3$$, use $$f(x) = \frac{x}{x + 3}$$:
- At $$x=3.1$$, $$f(3.1) = \frac{3.1}{6.1} \approx 0.508197$$
- At $$x=3.05$$, $$f(3.05) = \frac{3.05}{6.05} \approx 0.504132$$
- At $$x=3.01$$, $$f(3.01) = \frac{3.01}{6.01} \approx 0.500832$$
- At $$x=3.001$$, $$f(3.001) = \frac{3.001}{6.001} \approx 0.500083$$
- At $$x=3.0001$$, $$f(3.0001) = \frac{3.0001}{6.0001} \approx 0.500008$$
- At $$x=2.9$$, $$f(2.9) = \frac{2.9}{5.9} \approx 0.491525$$
- At $$x=2.95$$, $$f(2.95) = \frac{2.95}{5.95} \approx 0.495798$$
- At $$x=2.99$$, $$f(2.99) = \frac{2.99}{5.99} \approx 0.499166$$
- At $$x=2.999$$, $$f(2.999) = \frac{2.999}{5.999} \approx 0.499916$$
- At $$x=2.9999$$, $$f(2.9999) = \frac{2.9999}{5.9999} \approx 0.499992$$
Values approach approximately 0.5.
(b) For $$x \to -3$$, use the same simplified function:
- At $$x=-2.5$$, $$f(-2.5) = \frac{-2.5}{0.5} = -5.000000$$
- At $$x=-2.9$$, $$f(-2.9) = \frac{-2.9}{0.1} = -29.000000$$
- At $$x=-2.95$$, $$f(-2.95) = \frac{-2.95}{0.05} = -59.000000$$
- At $$x=-2.99$$, $$f(-2.99) = \frac{-2.99}{0.01} = -299.000000$$
- At $$x=-2.999$$, $$f(-2.999) = \frac{-2.999}{0.001} = -2999.000000$$
- At $$x=-2.9999$$, $$f(-2.9999) = \frac{-2.9999}{0.0001} = -29999.000000$$
- At $$x=-3.5$$, $$f(-3.5) = \frac{-3.5}{-0.5} = 7.000000$$
- At $$x=-3.1$$, $$f(-3.1) = \frac{-3.1}{-0.1} = 31.000000$$
- At $$x=-3.05$$, $$f(-3.05) = \frac{-3.05}{-0.05} = 61.000000$$
- At $$x=-3.01$$, $$f(-3.01) = \frac{-3.01}{-0.01} = 301.000000$$
- At $$x=-3.001$$, $$f(-3.001) = \frac{-3.001}{-0.001} = 3001.000000$$
- At $$x=-3.0001$$, $$f(-3.0001) = \frac{-3.0001}{-0.0001} = 30001.000000$$
Values approach $$-\infty$$ from the right side and $$+\infty$$ from the left side, so the limit does not exist.
4. **Conclusion:**
(a) $$\lim_{x \to 3} \frac{x^2 - 3x}{x^2 - 9} = 0.5$$
(b) $$\lim_{x \to -3} \frac{x^2 - 3x}{x^2 - 9}$$ does not exist because the left and right limits diverge to $$+\infty$$ and $$-\infty$$ respectively.