Derivative Evaluation 5A2568
1. **Problem (a):** Evaluate $\frac{dy}{dx}$ at $x=2.5$ for $y=\frac{2x^2+3}{\ln(2x)}$.
2. **Formula and rules:** Use the quotient rule for derivatives: if $y=\frac{u}{v}$, then
$$\frac{dy}{dx} = \frac{v\frac{du}{dx} - u\frac{dv}{dx}}{v^2}$$
where $u=2x^2+3$ and $v=\ln(2x)$.
3. **Calculate derivatives:**
- $\frac{du}{dx} = 4x$
- $\frac{dv}{dx} = \frac{1}{2x} \times 2 = \frac{1}{x}$ (chain rule on $\ln(2x)$)
4. **Apply quotient rule:**
$$\frac{dy}{dx} = \frac{\ln(2x) \cdot 4x - (2x^2+3) \cdot \frac{1}{x}}{(\ln(2x))^2}$$
5. **Simplify numerator:**
$$4x \ln(2x) - \frac{2x^2+3}{x} = 4x \ln(2x) - 2x - \frac{3}{x}$$
6. **Evaluate at $x=2.5$:**
- $\ln(2 \times 2.5) = \ln(5) \approx 1.60944$
- Numerator: $4 \times 2.5 \times 1.60944 - 2 \times 2.5 - \frac{3}{2.5} = 16.0944 - 5 - 1.2 = 9.8944$
- Denominator: $(1.60944)^2 = 2.5903$
7. **Final value:**
$$\frac{dy}{dx} = \frac{9.8944}{2.5903} \approx 3.82$$ (3 significant figures)
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**Answer (a):** $\boxed{3.82}$
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**Slug:** derivative evaluation
**Subject:** calculus
**Desmos:** {"latex":"y=\frac{2x^2+3}{\ln(2x)}","features":{"intercepts":true,"extrema":true}}
**q_count:** 4