To transform the function \( f(x) = 4^x - 5 \) to \( f(x) = 4^{2^x} - 5 \), we can observe the exponential term.
- The original function is \( 4^x \).
- The transformed function is \( 4^{2^x} \).
This transformation involves replacing \( x \) with \( 2^x \).
This indicates that the function is experiencing a change in its input that is nonlinear. The transformation from using \( x \) to \( 2^x \) suggests that the graph of the function will stretch vertically.
Now, to identify the value of \( k \) in the context, we have:
- The transformation related to \( 2^x \) indicates that the function is stretched because it is growing at a rate that is faster than a linear transformation.
Thus, the answer is:
2; stretch