1. **Problem statement:** Find the intercepts, asymptotes, critical points, intervals of increase/decrease, inflection points, concavity, and relative extrema for the function $$y = -\frac{x^3}{x^2 - 4}$$.
2. **Find x- and y-intercepts:**
- x-intercepts occur when $$y=0$$, so numerator $$-x^3=0 \Rightarrow x=0$$.
- y-intercept is $$y(0) = -\frac{0}{0-4} = 0$$.
3. **Find vertical asymptotes:**
- Denominator $$x^2 - 4 = 0 \Rightarrow x=\pm 2$$.
- Vertical asymptotes at $$x=2$$ and $$x=-2$$.
4. **Find horizontal/slant asymptotes:**
- Degree numerator = 3, denominator = 2, so slant asymptote.
- Perform polynomial division:
$$\frac{-x^3}{x^2 - 4} = -x - \frac{4x}{x^2 - 4}$$
- As $$x \to \pm \infty$$, $$y \sim -x$$.
- Slant asymptote: $$y = -x$$.
5. **Find critical points:**
- Compute derivative using quotient rule:
$$y = -\frac{x^3}{x^2 - 4}$$
$$y' = \frac{-(3x^2)(x^2 - 4) - (-x^3)(2x)}{(x^2 - 4)^2} = \frac{-3x^2(x^2 - 4) + 2x^4}{(x^2 - 4)^2}$$
- Simplify numerator:
$$-3x^4 + 12x^2 + 2x^4 = (-3x^4 + 2x^4) + 12x^2 = -x^4 + 12x^2$$
- So:
$$y' = \frac{-x^4 + 12x^2}{(x^2 - 4)^2} = \frac{-x^2(x^2 - 12)}{(x^2 - 4)^2}$$
- Set numerator zero:
$$-x^2(x^2 - 12) = 0 \Rightarrow x=0 \text{ or } x=\pm \sqrt{12} = \pm 2\sqrt{3}$$
- Critical points at $$x=0, \pm 2\sqrt{3}$$.
6. **Determine intervals of increase/decrease:**
- Denominator always positive except at vertical asymptotes.
- Sign of $$y'$$ depends on numerator:
- For $$|x| < 2\sqrt{3}$$, $$x^2 - 12 < 0$$, so numerator $$-x^2(x^2 - 12) > 0$$ (since $$-x^2$$ is negative, times negative is positive).
- For $$|x| > 2\sqrt{3}$$, numerator negative.
- So:
- Increasing on $$(-2,0) \cup (0, 2\sqrt{3})$$
- Decreasing on $$(-\infty, -2\sqrt{3}) \cup (2\sqrt{3}, -2)$$ but note vertical asymptotes at $$\pm 2$$ split intervals.
7. **Find inflection points:**
- Compute second derivative (omitted detailed algebra for brevity):
$$y'' = \frac{d}{dx} y'$$
- Inflection points occur where $$y''=0$$ or undefined (excluding vertical asymptotes).
- After simplification, inflection points at $$x=\pm 2$$ (vertical asymptotes) and $$x=0$$.
8. **Concavity intervals:**
- Using sign of $$y''$$, function is concave up where $$y'' > 0$$ and concave down where $$y'' < 0$$.
- Analysis shows concave up on $$(-\infty, -2) \cup (0, 2)$$ and concave down on $$(-2, 0) \cup (2, \infty)$$.
9. **Relative minima and maxima:**
- Use first derivative test at critical points:
- At $$x=0$$, derivative changes from positive to positive (no extremum).
- At $$x=-2\sqrt{3}$$, derivative changes from negative to positive (relative minimum).
- At $$x=2\sqrt{3}$$, derivative changes from positive to negative (relative maximum).
**Final summary:**
- x-intercept and y-intercept at $$0$$.
- Vertical asymptotes at $$x=\pm 2$$.
- Slant asymptote $$y = -x$$.
- Critical points at $$x=0, \pm 2\sqrt{3}$$.
- Increasing on $$(-2,0) \cup (0, 2\sqrt{3})$$.
- Decreasing on $$(-\infty, -2\sqrt{3}) \cup (2\sqrt{3}, -2)$$.
- Inflection points at $$x=0$$.
- Concave up on $$(-\infty, -2) \cup (0, 2)$$.
- Concave down on $$(-2, 0) \cup (2, \infty)$$.
- Relative minimum at $$x=-2\sqrt{3}$$.
- Relative maximum at $$x=2\sqrt{3}$$.
Rational Function 22 0A6C04
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