In part (a), the inverse function of $f(x) = 2x - 6$ was correctly found to be:

$f^{-1}(x) = \frac{x + 6}{2}$

For part (b), the graphs of a function and its inverse are symmetric with respect to the line $y = x$. This is a general property of inverse functions.

Thus, the answer for part (b) is:

$y = x$

Would you like further details or have any other questions?

Here are five related questions to deepen your understanding:

1. How do you verify if two functions are inverses of each other?
2. Can you explain why the symmetry between $f(x)$ and $f^{-1}(x)$ occurs along the line $y = x$?
3. What is the graphical interpretation of an inverse function?
4. How do you determine if a function has an inverse function?
5. What happens if a function is not one-to-one? Can it still have an inverse?

Tip: To check if two functions are inverses, compose them (i.e., find $f(f^{-1}(x))$ and $f^{-1}(f(x))$) and verify that both simplify to $x$.