Identifying Exponential Growth or Decay in (e^4-x) + 2

In summary, the provided function, f(x) = e^(4-x) + 2, is an exponential decay function. This can be shown by using the formula f(x) = ae^kx, where a>0 and k<0. In this case, a=1 and k=-1, indicating a decay rate of -1. Additionally, as x approaches negative infinity, the limit of the function approaches infinity, while as x approaches infinity, the limit approaches 2. This aligns with the definition of an exponential decay function.
  • #1
j9mom
31
0

Homework Statement



State whether (e^4-x) + 2 is an exponential growth function or an exponential decay function. Explain why.

Homework Equations



I want to use the formula f(x) = ae^kx where a>0, and k<0.

The Attempt at a Solution



I know it is an exponential decay formula because the limit as x goes to -inf. = inf. and the limit as x goes to inf. = 2. But I do not know how to describe what a and k are in this equation to show it is an exponential decay function.
 
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  • #2
Ok, would I just say the parent function is f(x) = e^-1x so a is 1 and k is -1. Then the function is shifted up 2, to the left 4?
 
  • #3
j9mom said:

Homework Statement



State whether (e^4-x) + 2 is an exponential growth function or an exponential decay function. Explain why.
What you wrote is e4 - x + 2, which is a straight line whose slope is -1.

Did you mean e-4x + 2? If so, the parentheses need to be around the exponent, not the exponential expression. IOW, like this: e^(-4x) + 2.
j9mom said:

Homework Equations



I want to use the formula f(x) = ae^kx where a>0, and k<0.
You need parentheses here, too. f(x) = ae^(kx).
j9mom said:

The Attempt at a Solution



I know it is an exponential decay formula because the limit as x goes to -inf. = inf. and the limit as x goes to inf. = 2. But I do not know how to describe what a and k are in this equation to show it is an exponential decay function.
 
  • #4
Yes, I did mean to type f(x) = e^(4-x) + 2

and f(x) = ae^(-kx)

Thank you for that correction
 
  • #5
e4 - x = e4 * e-x = ##\frac{e^4}{e^x}##
 
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1. What is exponential growth or decay?

Exponential growth or decay is a mathematical concept that describes a rapid increase or decrease in a quantity over time, where the rate of change is proportional to the current value of the quantity.

2. How is exponential growth or decay different from linear growth or decay?

In linear growth or decay, the quantity changes at a constant rate over time. In exponential growth or decay, the rate of change increases or decreases as the quantity increases or decreases, resulting in a rapidly accelerating or decelerating trend.

3. What are some real-world examples of exponential growth or decay?

Examples of exponential growth include population growth, compound interest in finance, and the spread of infectious diseases. Examples of exponential decay include radioactive decay and the decrease in value of a car over time.

4. How is exponential growth or decay calculated?

The formula for exponential growth is y = ab^x, where a is the initial quantity, b is the growth rate, and x is the time. The formula for exponential decay is y = ab^(-x), where a is the initial quantity, b is the decay rate, and x is the time.

5. What factors can affect the rate of exponential growth or decay?

The rate of exponential growth or decay can be affected by various factors such as the initial quantity, the growth or decay rate, and external influences like competition, resources, and limiting factors. Additionally, for exponential decay, the half-life of the quantity is an important factor that determines the rate of decay.

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