Derivative Practice
1. **Problem Statement:** Find the derivative $f'(x)$ for the function $f(x) = x + \sqrt{x}$.
2. **Recall the derivative rules:** The derivative of $x$ is 1. For $\sqrt{x}$, rewrite as $x^{1/2}$ and use the power rule: $\frac{d}{dx} x^n = n x^{n-1}$.
3. **Apply the derivative:**
$$f'(x) = \frac{d}{dx} x + \frac{d}{dx} x^{1/2} = 1 + \frac{1}{2} x^{-1/2} = 1 + \frac{1}{2\sqrt{x}}.$$
4. **Problem Statement:** Find $f'(x)$ for $f(x) = 2 + \frac{1}{x} + \frac{1}{x^2}$.
5. **Rewrite terms:** $\frac{1}{x} = x^{-1}$ and $\frac{1}{x^2} = x^{-2}$.
6. **Apply power rule:**
$$f'(x) = 0 - x^{-2} - 2x^{-3} = -\frac{1}{x^2} - \frac{2}{x^3}.$$
7. **Problem Statement:** Find $f'(x)$ for $f(x) = \sqrt{x} \cos(x)$.
8. **Use product rule:** $\frac{d}{dx} [u v] = u' v + u v'$, where $u = \sqrt{x} = x^{1/2}$ and $v = \cos(x)$.
9. **Derivatives:**
$u' = \frac{1}{2} x^{-1/2}$,
$v' = -\sin(x)$.
10. **Apply product rule:**
$$f'(x) = \frac{1}{2} x^{-1/2} \cos(x) - x^{1/2} \sin(x).$$
11. **Problem Statement:** Find $f'(x)$ for $f(x) = x^3 e^x$.
12. **Use product rule:** $u = x^3$, $v = e^x$,
$u' = 3x^2$, $v' = e^x$.
13. **Apply product rule:**
$$f'(x) = 3x^2 e^x + x^3 e^x = e^x (3x^2 + x^3).$$
14. **Problem Statement:** Find $f'(x)$ for $f(x) = \frac{x^3}{e^x}$.
15. **Rewrite:** $f(x) = x^3 e^{-x}$.
16. **Use product rule:** $u = x^3$, $v = e^{-x}$,
$u' = 3x^2$, $v' = -e^{-x}$.
17. **Apply product rule:**
$$f'(x) = 3x^2 e^{-x} - x^3 e^{-x} = e^{-x} (3x^2 - x^3).$$
18. **Problem Statement:** Find $f'(x)$ for $f(x) = (3x^2 + 2x + 1)^5$.
19. **Apply chain rule:** Let $u = 3x^2 + 2x + 1$, then $f(x) = u^5$.
20. **Derivatives:**
$g(u) = u^5$, so $g'(u) = 5u^4$.
$u'(x) = 6x + 2$.
21. **Apply chain rule:**
$$f'(x) = g'(u) \cdot u'(x) = 5(3x^2 + 2x + 1)^4 (6x + 2).$$
**Final answers:**
1) $f'(x) = 1 + \frac{1}{2\sqrt{x}}$
2) $f'(x) = -\frac{1}{x^2} - \frac{2}{x^3}$
3) $f'(x) = \frac{1}{2} x^{-1/2} \cos(x) - x^{1/2} \sin(x)$
4) $f'(x) = e^x (3x^2 + x^3)$
5) $f'(x) = e^{-x} (3x^2 - x^3)$
6) $f'(x) = 5(3x^2 + 2x + 1)^4 (6x + 2)$