Derivative Radical
1. **State the problem:** Find the derivative $\frac{dy}{dx}$ of the function $y = -12\sqrt{x^3 + 7x - 1}$.
2. **Recall the formula:** For $y = k\sqrt{u}$ where $u$ is a function of $x$, rewrite as $y = k u^{1/2}$. The derivative is given by the chain rule:
$$\frac{dy}{dx} = k \cdot \frac{1}{2} u^{-1/2} \cdot \frac{du}{dx}$$
3. **Identify $u$ and $k$:** Here, $k = -12$ and $u = x^3 + 7x - 1$.
4. **Compute $\frac{du}{dx}$:**
$$\frac{du}{dx} = 3x^2 + 7$$
5. **Apply the chain rule:**
$$\frac{dy}{dx} = -12 \cdot \frac{1}{2} (x^3 + 7x - 1)^{-1/2} (3x^2 + 7)$$
6. **Simplify constants:**
$$\frac{dy}{dx} = -6 (x^3 + 7x - 1)^{-1/2} (3x^2 + 7)$$
7. **Rewrite in radical form:**
$$\frac{dy}{dx} = \frac{-6 (3x^2 + 7)}{\sqrt{x^3 + 7x - 1}}$$
**Final answer:**
$$\boxed{\frac{dy}{dx} = \frac{-6 (3x^2 + 7)}{\sqrt{x^3 + 7x - 1}}}$$