MCQ
If ${I_n} = \int_0^\infty {{e^{ - x}}{x^{n - 1}}dx,} $ then $\int_0^\infty {{e^{ - \lambda x}}{x^{n - 1}}dx = } $
  • A
    $\lambda {I_n}$
  • B
    $\frac{1}{\lambda }{I_n}$
  • $\frac{{{I_n}}}{{{\lambda ^n}}}$
  • D
    ${\lambda ^n}{I_n}$

Answer

Correct option: C.
$\frac{{{I_n}}}{{{\lambda ^n}}}$
c
(c) Putting $\lambda x = t,\lambda dx = dt$

we get , $\int_0^\infty {{e^{ - \lambda x}}{x^{n - 1}}dx} $

$ = \frac{1}{{{\lambda ^n}}}\int_0^\infty {{e^{ - t}}{t^{n - 1}}} dt$

$ = \frac{1}{{{\lambda ^n}}}\int_0^\infty {{e^{ - x}}{x^{n - 1}}dx = \frac{{{I_n}}}{{{\lambda ^n}}}} $.

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