Find Value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)

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In summary, the problem says y=f(x) and find the value of \(\int_{-\infty}^{\infty}f(x)dx\) if it converges. The integral diverges since the exponential term goes to \(0\) as \(x\) becomes large.
  • #1
Nicole18
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the problem says \(y=f(x)\) and find the value of \(\int_{-\infty}^{\infty}f(x)dx\) if it converges

\[f(x)=\begin{cases}2-e^{-0.2x}&\text{ for } x \ge 0\\0&\text{
otherwise} \end{cases}\]...help
 
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  • #2
Nicole18 said:
the problem says y=f(x) and find the value of negative to positive infinityf(x)dx if it converges

f(x)={2-e^-.2x
{0
x is greater than or equal to 0
otherwise
...help

Hi Nicole18,

Welcome to MHB. :)

Can you edit your post a bit? It's hard to fully understand what you mean. The first line could be $f(x)={2-e^{-.2}}x$ or $f(x)={2-e^{-.2x}}$. The second and third lines don't make any sense to me. What is greater than or equal to 0? Line 2? Line 1? Something else?

Lastly is this an integral or a sum?

Jameson
 
  • #3
Nicole18 said:
the problem says y=f(x) and find the value of negative to positive infinityf(x)dx if it converges

f(x)={2-e^-.2x
{0
x is greater than or equal to 0
otherwise
...help

Welcome on MHB Nicole!...

If You want to receive a precise answer You have to do a precise question. First : f(x) is like that... $\displaystyle f(x) = \begin{cases} 2-e^{- .2\ x}\ \text{if } x \ge 0\\
0\ \text{otherwise} \end{cases}$ (1)

... or some else?... Second: do You ask if ... $\displaystyle \int_{- \infty}^{+ \infty} f(x)\ dx$ (2) ... converges and if yes to what it converges?... Kind regards $\chi$ $\sigma$ P.S. If You click on 'replay with quote' You can have a good example of use of LaTex...
 
  • #4
yes the way chisigma wrote it is correct...i really have no idea how to even start this i need a precise answer. how do i tell if it converges i know converges means it is getting close to a number
 
  • #5
Nicole18 said:
yes the way chisigma wrote it is correct...i really have no idea how to even start this i need a precise answer. how do i tell if it converges i know converges means it is getting close to a number

Very well!... we can write thye integral as $I= I_{1}+ I_{2}$ where... $\displaystyle I_{1} = \int_{0}^{\infty} 2\ dx$ (1)$\displaystyle I_{2}= - \int_{0}^{\infty} e^{- \frac{x}{5}}\ dx$ (2)

Starting from the second we have...

$\displaystyle I_{2} = \lim_{t \rightarrow \infty} - \int_{0}^{t} e^{- \frac{x}{5}}\ dx = \lim_{t \rightarrow \infty} 5\ |e^{- \frac{x}{5}}|_{0}^{t} = - 5$ (3)

... a now the first...

$\displaystyle I_{1} = \lim_{t \rightarrow \infty} \int_{0}^{t} 2\ dx = \lim_{t \rightarrow \infty} 2 |x|_{0}^{t} = + \infty$ (4)

The conclusion is: the integral doesn't converge...

Kind regards

$\chi$ $\sigma$
 
  • #6
Nicole18 said:
the problem says \(y=f(x)\) and find the value of \(\int_{-\infty}^{\infty}f(x)dx\) if it converges

\[f(x)=\begin{cases}2-e^{-0.2x}&\text{ for } x \ge 0\\0&\text{
otherwise} \end{cases}\]...help
The integral diverges since the exponential term goes to \(0\) as \(x\) becomes large, so the right tail of the integral is like the integral of a non zero constant (and of course the left tail converges since the integrand is zero for \(x\lt 0\).

CB
 

FAQ: Find Value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)

What is the meaning of the integral \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)?

The integral \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\) represents the area under the curve of the function \(f(x)\) from negative infinity to positive infinity. It is a way to measure the total value or total change of a function over a certain interval.

What does it mean to find the value of \(\int_{-\infty}^{\infty} f(x) dx\) for a specific function \(f(x)\)?

Finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for a specific function \(f(x)\) means calculating the numerical value of the integral, which represents the total area under the curve of the function from negative infinity to positive infinity. This value can be used to analyze the behavior of the function or to solve certain problems in mathematics and physics.

What are the different methods for finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)?

There are several methods for finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\), such as the Fundamental Theorem of Calculus, integration by parts, substitution, and partial fractions. The choice of method depends on the complexity of the function and the problem at hand.

What are the applications of finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)?

Finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\) has various applications in mathematics, physics, and engineering. It can be used to calculate the area under a curve, the volume of a solid, the work done by a force, the probability of an event, and many other quantities in real-life situations.

What are the common mistakes to avoid when finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\)?

Some common mistakes to avoid when finding the value of \(\int_{-\infty}^{\infty} f(x) dx\) for \(y=f(x)\) include forgetting to include the limits of integration, making algebraic errors while evaluating the integral, and not simplifying the result to its simplest form. It is important to carefully follow the steps of the chosen method and to check the final answer for accuracy.

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