MCQ
The remainder on dividing $1+3+3^{2}+3^{3}+\ldots+3^{2021}$ by $50$ is
- A$5$
- ✓$4$
- C$2$
- D$6$
$=\frac{(10-1)^{1011}-1}{2}$
$=\frac{100 \lambda+10110-1-1}{2}$
$=50 \lambda+\frac{10108}{2}$
$=50 \lambda+5054$
$=50 \lambda+50 \times 101+4$
$\operatorname{Rem}(50)=4 .$
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$I=\int_{0}^{10} \frac{[x] e^{[x]}}{e^{x-1}} d x,$
where $[ x ]$ denotes the greatest integer less than or equal to $x$. Then the value of $I$ is equal to:
$f(x)=3 \log _{e}\left|\frac{x-1}{x+1}\right|-\frac{2}{x-1}$
Then in which of the following intervals, function $f ( x )$ is increasing?