Step 1: Differentiating the given equation.
We are given the equation \( \sqrt{\frac{x}{y}} + \sqrt{\frac{y}{x}} = 4 \). To differentiate this implicitly, we first rewrite the equation as:
\[
\frac{\sqrt{x}}{\sqrt{y}} + \frac{\sqrt{y}}{\sqrt{x}} = 4
\]
Now, differentiate both sides with respect to \( x \). Use the chain rule for each term.
Step 2: Simplifying the derivative.
After differentiating, we obtain the expression for \( \frac{dy}{dx} \):
\[
\frac{dy}{dx} = \frac{7y - x}{y - 7x}
\]
Step 3: Conclusion.
Thus, the value of \( \frac{dy}{dx} \) is \( \frac{7y - x}{y - 7x} \), which makes option (B) the correct answer.