Answer:
![f(x) = 4(\frac{2}{3})^{x}](https://tex.z-dn.net/?f=f%28x%29%20%3D%204%28%5Cfrac%7B2%7D%7B3%7D%29%5E%7Bx%7D)
Step-by-step explanation:
The first function is given as,
.
Now, the value of this function increases i.e. value of f(x) increases as the x-value increases because
.
Now, the second function is given as,
.
This function can not be considered as a continuous function because
.
Again, the third function is given as,
.
This function can also not be considered as a continuous function because
.
Finally, the fourth function is given to be,
.
In this function, the value of f(x) continuously decreases as the value of x increases, because
.
Therefore, this function represents exponential decay. (Answer)