Determine if each of the following functions is a growth exponential or a decay exponential.

To determine whether each function is a growth or decay exponential, you can look at the base of the exponent:

- If the base is greater than 1, it represents exponential growth.
- If the base is between 0 and 1, it represents exponential decay.
- If the base is negative, additional information regarding the context is needed, but typically we consider real bases.

Let's analyze each function provided:

a. \( y = 0.8^{2x} \)
- The base is 0.8, which is less than 1.
- **Conclusion:** This is a **decay** exponential.

b. \( y = 2^{-1.8x} \)
- The base is \( 2 \), which is greater than 1, but since the exponent is negative (\(-1.8x\)), it represents decay.
- **Conclusion:** This is a **decay** exponential.

c. \( y = 4^{0.4x} \)
- The base is \( 4\), which is greater than 1.
- **Conclusion:** This is a **growth** exponential.

d. \( y = 3 e^{-3x} \)
- The base is \( e \approx 2.718\), which is greater than 1, but the exponent is negative (\(-3x\)), indicating decay as well.
- **Conclusion:** This is a **decay** exponential.

So, to summarize:

- a. Decay
- b. Decay
- c. Growth
- d. Decay