To find the inverse of the function \( f(x) = 6x^2 + 12 \) with the domain restricted to \( x \geq 0 \), we can follow these steps:
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Replace \( f(x) \) with \( y \): \[ y = 6x^2 + 12 \]
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Swap \( x \) and \( y \): \[ x = 6y^2 + 12 \]
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Solve for \( y \): \[ x - 12 = 6y^2 \] \[ y^2 = \frac{x - 12}{6} \] \[ y = \sqrt{\frac{x - 12}{6}} \quad (\text{since } y \geq 0 \text{ because the domain of } f \text{ is } x \geq 0) \]
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Write the inverse function: \[ f^{-1}(x) = \sqrt{\frac{x - 12}{6}} \]
Now, let's analyze the answer choices provided:
- \( f^{-1}(x) = \frac{x}{6} - 2 \)
- \( f^{-1}(x) = \sqrt{x} - 12 \)
- \( f^{-1}(x) = \frac{x}{6} + 2 \)
- \( f^{-1}(x) = \sqrt{x} - 12 \)
- \( f^{-1}(x) = \sqrt{\frac{x - 12}{6}} \)
The correct choice corresponds to \( f^{-1}(x) = \sqrt{\frac{x - 12}{6}} \).
Thus, the inverse function is:
\[ \boxed{f^{-1}(x) = \sqrt{\frac{x - 12}{6}}} \]