Chapter 12 - Exponential Functions and Logarithmic Functions - 12.2 Exponential Functions - 12.2 Exercise Set - Page 795: 6

True.

All graphs of $f(x)=a^{x}$ have the $x$-axis as the horizontal asymptote. Swapping x and y produces a graph that is reflected about the line $y=x,$ so it will have the y-axis as the asymptote. (Asymptote = a line that the graph approaches, but never touches.) The statement is true.