Derivative Rational Minimum B53202
1. **Problem 1:** Find $f'(2)$ for $f(x) = \sqrt{6 - x}$.
- The function can be rewritten as $f(x) = (6 - x)^{\frac{1}{2}}$.
- Using the chain rule, the derivative is
$$f'(x) = \frac{1}{2}(6 - x)^{-\frac{1}{2}} \cdot (-1) = -\frac{1}{2\sqrt{6 - x}}.$$
- Evaluate at $x=2$:
$$f'(2) = -\frac{1}{2\sqrt{6 - 2}} = -\frac{1}{2\sqrt{4}} = -\frac{1}{2 \cdot 2} = -\frac{1}{4}.$$
2. **Problem 2:** Solve the equation
$$\frac{1}{x-2} = \frac{3}{x+2} - \frac{6x}{x^2 - 4}.$$
- Note that $x^2 - 4 = (x-2)(x+2)$.
- Rewrite the right side with common denominator $(x-2)(x+2)$:
$$\frac{3}{x+2} = \frac{3(x-2)}{(x+2)(x-2)}, \quad \frac{6x}{x^2 - 4} = \frac{6x}{(x-2)(x+2)}.$$
- So the equation becomes
$$\frac{1}{x-2} = \frac{3(x-2) - 6x}{(x-2)(x+2)} = \frac{3x - 6 - 6x}{(x-2)(x+2)} = \frac{-3x - 6}{(x-2)(x+2)}.$$
- Multiply both sides by $(x-2)(x+2)$ (excluding $x=\pm 2$):
$$(x+2) = -3x - 6.$$
- Solve for $x$:
$$x + 2 = -3x - 6 \implies x + 3x = -6 - 2 \implies 4x = -8 \implies x = -2.$$
- Check domain restrictions: $x \neq \pm 2$, so $x = -2$ is excluded.
- No solution remains, so the solution set is empty $\emptyset$.
3. **Problem 3:** Identify the local minimum point of
$$f(x) = -3x^4 + 4x^3 + 12x^2 + 1.$$
- Find the first derivative:
$$f'(x) = -12x^3 + 12x^2 + 24x.$$
- Set $f'(x) = 0$:
$$-12x^3 + 12x^2 + 24x = 0 \implies -12x^3 + 12x^2 + 24x = 0.$$
- Factor out $-12x$:
$$-12x(x^2 - x - 2) = 0.$$
- Solve factors:
$$-12x = 0 \implies x=0,$$
$$x^2 - x - 2 = 0 \implies (x-2)(x+1) = 0 \implies x=2 \text{ or } x=-1.$$
- Find second derivative:
$$f''(x) = -36x^2 + 24x + 24.$$
- Evaluate $f''(x)$ at critical points:
- At $x=0$:
$$f''(0) = 24 > 0,$$ so local minimum at $x=0$.
- At $x=-1$:
$$f''(-1) = -36(1) + 24(-1) + 24 = -36 - 24 + 24 = -36 < 0,$$ local maximum.
- At $x=2$:
$$f''(2) = -36(4) + 24(2) + 24 = -144 + 48 + 24 = -72 < 0,$$ local maximum.
- Find $f(0)$:
$$f(0) = 1.$$
- So the local minimum point is $(0, 1)$.
**Final answers:**
1. $f'(2) = -\frac{1}{4}$.
2. Solution set is $\emptyset$.
3. Local minimum point is $(0, 1)$.