Given the following exponential function, identify whether the change represents growth or decay, and determine the percentage rate of increase or decrease per unit of [tex] x [/tex], to the nearest tenth of a percent.

[tex]\[ y = 1800 e^{\ln (0.87) x} \][/tex]

Is the change:

A. Growth
B. Decay

Determine the percentage rate of:

[tex] \% [/tex] increase/decrease per unit of [tex] x [/tex] (nearest tenth of a percent).



Answer :

To determine whether the given exponential function represents growth or decay, and the percentage rate of that change, we need to analyze the function in its standard exponential form.

Given:
[tex]\[ y = 1800e^{\ln(0.87)x} \][/tex]

### Step-by-Step Solution:

1. Identify the Exponential Base:
- The exponent part of the function is [tex]\( e^{\ln(0.87)x} \)[/tex].

2. Simplify the Exponent:
- Recall the property of logarithms: [tex]\( e^{\ln a} = a \)[/tex]. Here, we have [tex]\( \ln(0.87) \)[/tex], which can be rewritten as:
[tex]\[ y = 1800 \cdot (e^{\ln(0.87)})^x \][/tex]
[tex]\[ y = 1800 \cdot 0.87^x \][/tex]

3. Determine Growth or Decay:
- Notice the base 0.87. Since 0.87 is less than 1, the exponential function [tex]\( 0.87^x \)[/tex] represents exponential decay.

4. Calculate the Percentage Rate of Decrease:
- The decay rate can be found by recognizing that the base of 0.87 implies a decrease from 1.
- The percentage decrease per unit [tex]\( x \)[/tex] is calculated as:
[tex]\[ 1 - 0.87 = 0.13 \text{ (or 13%)} \][/tex]

### Conclusion:
The given function represents exponential decay, and the percentage rate of decrease per unit of [tex]\( x \)[/tex] is [tex]\( 13.0\% \)[/tex].

So the final answer is:
Decay [tex]\( \, \, 13.0\% \)[/tex] decrease