Question:

$\int\limits_{0}^{1} x e^{-5x} \, dx$ is equal to

Updated On: Jul 9, 2024
  • $\frac{1}{25}-\frac{6e^{-5}}{25}$
  • $\frac{1}{25}+\frac{6e^{-5}}{25}$
  • $-\frac{1}{25}-\frac{6e^{-5}}{25}$
  • $\frac{1}{25}-\frac{1}{5}e^{-5}$
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The Correct Option is A

Solution and Explanation

$\int_{0}^{1} \,\underset{I}{x}\, \underset{II}{e^{-5x}}\,dx$
$=\left[\left\{x\left(\frac{e^{-5 x}}{-5}\right)\right\}\right]_{0}^{1}-\left\{\int_{0}^{1} 1 \cdot \frac{e^{-5 x}}{-5} d x\right\}$
$=\left[-\frac{x e^{-5 x}}{5}-\frac{e^{-5 x}}{25}\right]_{0}^{1}$
$=-\frac{e^{-5}}{5}-\frac{e^{-5}}{25}+\frac{1}{25}$
$=-\frac{6 e^{-5}}{25}+\frac{1}{25}=\frac{1}{25}-\frac{6 e^{-5}}{25}$
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Concepts Used:

Integrals of Some Particular Functions

There are many important integration formulas which are applied to integrate many other standard integrals. In this article, we will take a look at the integrals of these particular functions and see how they are used in several other standard integrals.

Integrals of Some Particular Functions:

  • ∫1/(x2 – a2) dx = (1/2a) log|(x – a)/(x + a)| + C
  • ∫1/(a2 – x2) dx = (1/2a) log|(a + x)/(a – x)| + C
  • ∫1/(x2 + a2) dx = (1/a) tan-1(x/a) + C
  • ∫1/√(x2 – a2) dx = log|x + √(x2 – a2)| + C
  • ∫1/√(a2 – x2) dx = sin-1(x/a) + C
  • ∫1/√(x2 + a2) dx = log|x + √(x2 + a2)| + C

These are tabulated below along with the meaning of each part.