Which of the following functions is an example of exponential growth?

I. [tex]\( f(x) = \frac{1}{4}\left(\frac{1}{2}\right)^x \)[/tex]
II. [tex]\( f(x) = 2\left(3^x\right) \)[/tex]
III. [tex]\( f(x) = 5\left(\frac{1}{2}\right)^x \)[/tex]

A. II and III only
B. II only
C. I and III only
D. I and II only



Answer :

To determine which of the given functions are examples of exponential growth, let's analyze each function individually.

### Function I:
[tex]\[ f(x) = \frac{1}{4} \left( \frac{1}{2} \right)^x \][/tex]
In this function, the base of the exponent is [tex]\( \frac{1}{2} \)[/tex].

- Exponential growth occurs when the base of the exponent is greater than 1.
- Here, [tex]\( \frac{1}{2} < 1 \)[/tex].
- A base less than 1 indicates exponential decay, not growth.

Hence, Function I is not an example of exponential growth.

### Function II:
[tex]\[ f(x) = 2 \left( 3^x \right) \][/tex]
In this function, the base of the exponent is [tex]\( 3 \)[/tex].

- Exponential growth occurs when the base of the exponent is greater than 1.
- Here, [tex]\( 3 > 1 \)[/tex], which means the function will grow exponentially as [tex]\( x \)[/tex] increases.

Hence, Function II is an example of exponential growth.

### Function III:
[tex]\[ f(x) = 5 \left( \frac{1}{2} \right)^x \][/tex]
In this function, the base of the exponent is [tex]\( \frac{1}{2} \)[/tex].

- Similar to Function I, a base of [tex]\( \frac{1}{2} \)[/tex] indicates exponential decay, not growth.
- Since [tex]\( \frac{1}{2} < 1 \)[/tex], the function decreases as [tex]\( x \)[/tex] increases.

Hence, Function III is not an example of exponential growth.

Based on our analysis, only Function II represents exponential growth. Therefore, the correct answer is:

B. II only