Q. $\int_{0}^{\infty}{\left\lbrack \frac{\lbrack x + 1\rbrack}{e^{x}} \right\rbrack dx}$ (where $\lbrack \bullet \rbrack$ denotes greatest integer function) is equal to

A) 0
B) 1
C) $\infty$
D) None of these
Explanation

(a)
$\frac{x + 1}{e^{x}} < 1$ …(i)
$\Rightarrow \ \frac{\lbrack x + 1\rbrack}{e^{x}} < 1$ …(ii)
(as $\lbrack x + 1\rbrack < x + 1$)
$\therefore\ \left\lbrack \frac{\lbrack x + 1\rbrack}{e^{x}} \right\rbrack = 0$ [from Eqs.(i) and (ii)]

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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