Short Answer
The problem involves identifying an exponential function that reveals the constant k when x equals 1. After evaluating the provided functions, it is determined that f(x) = 128(1.6)^(x-1) satisfies this requirement, clearly displaying k as 128.
Step 1: Understand the Problem
The problem requires identifying which exponential function allows the constant k to be displayed as either the coefficient or the base when the input x equals 1. We are specifically looking for a function that simplifies to k when evaluated at x = 1.
Step 2: Evaluate Each Function
We will substitute x = 1 into each of the given functions to check which function directly shows k. The functions to evaluate are:
- f(x) = 50(1.6)^(x+1)
- f(x) = 80(1.6)^(x)
- f(x) = 128(1.6)^(x-1)
- f(x) = 204.8(1.6)^(x-2)
By evaluating these, we find that only one of them yields k as a clear output.
Step 3: Identify the Correct Function
After evaluating, we find:
- For f(x) = 128(1.6)^(x-1), substituting x=1 gives f(1) = 128(1.6)^0 = 128, directly showing k.
- The other functions either change k through multiplication with the base or exponent, failing to display it directly.
Therefore, the function that displays k clearly is f(x) = 128(1.6)^(x-1).