Solving Improper Integral $\int_{-\infty}^{0}e^{-|x|}dx

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In summary, the conversation discusses the integral of e^-|x| over the negative half of the real line. The solution states that the integral is equivalent to e^x, but the individual is confused as they get e^-x and the final answer of -1. The discrepancy is due to the definition of |x|, which is equal to x for x >= 0 and -x for x < 0. The correct answer is 1, and the individual requests clarification on the simplification process.
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KingSloth
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Homework Statement



[tex]$\int_{-\infty}^{0}e^{-|x|}dx[/tex]

Homework Equations



[tex]$\int_{-\infty}^{0}e^{-|x|}dx[/tex]
= [tex]$\int_{-\infty}^{0}e^{-x}dx[/tex]

according to the solution these first two steps is where i go wrong. According to solution, the integral is e^x, which I don't understand. I get e^-x and when I carry out the problem I get -1. The correct answer is 1. Please explain the simplification. thank you
 
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  • #2
|x| is defined to be equal to x, if x >= 0, and to -x, if x < 0. Your interval over which your are integrating is the negative half of the real line.
 

What is an improper integral?

An improper integral is an integral where either the upper or lower limit of integration is infinite, or the integrand is not defined at one or more points within the interval of integration.

Why is the integral $\int_{-\infty}^{0}e^{-|x|}dx$ considered improper?

The integral is considered improper because the lower limit of integration is negative infinity, making it impossible to calculate the definite integral.

How do you solve an improper integral?

To solve an improper integral, you must first determine if it converges or diverges. If it converges, you can use the limit definition of an integral or any known integration techniques to evaluate it. If it diverges, you can use comparison tests or other convergence tests to determine the behavior of the integral.

What is the convergence behavior of $\int_{-\infty}^{0}e^{-|x|}dx$?

The integral $\int_{-\infty}^{0}e^{-|x|}dx$ converges absolutely, meaning that the integral converges regardless of the sign of the integrand. This can be shown by using the limit definition of an integral and evaluating the integral as the upper limit approaches negative infinity.

Can you evaluate $\int_{-\infty}^{0}e^{-|x|}dx$ exactly?

No, the integral $\int_{-\infty}^{0}e^{-|x|}dx$ cannot be evaluated exactly. However, it can be approximated using numerical methods such as the trapezoidal rule or Simpson's rule.

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