MCQ
A primitive of $f(x) = \frac{x}{{1 + {x^2}}}$ $dx$=
- A${\log _e}({x^2} + 1)$
- B$x{\tan ^{ - 1}}x$
- ✓$\frac{{{{\log }_e}({x^2} + 1)}}{2}$
- D$\frac{1}{2}x{\tan ^{ - 1}}x$
$\Rightarrow 2x\,dx = dt \Rightarrow x\,dx = dt2$
$\therefore \,\,\,I = \frac{1}{2}\int_{}^{} {\frac{{dt}}{t} = \frac{1}{2}\log t + c} $; $I = \frac{1}{2}\log (1 + {x^2}) + c$.
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$f(x) =$ $\left\{ {\begin{array}{*{20}{c}} {(x\, + \,1)\,\,{e^{ - \,\left[ {\tfrac{1}{{|x|}}\,\, + \,\,\tfrac{1}{x}} \right]}}}&{(x\,\, \ne \,\,0)} \\ {0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}&{(x\,\, = \,\,0)} \end{array}} \right.$
then which one of the following does not hold good ?