JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    If  \[g:[-2,\,2]\to R\]where \[g(x)=\] \[{{x}^{3}}+\tan x+\left[ \frac{{{x}^{2}}+1}{P} \right]\]is a odd function then the value of parametric P is            [DCE 2005]

    A)                    \[-5<P<5\]

    B)            \[P<5\]

    C)                    \[P>5\]

    D)            None of these

    Correct Answer: C

    Solution :

               \[g(x)={{x}^{3}}+\tan x+\frac{{{x}^{2}}+1}{P}\]                    \[g(-x)={{(-x)}^{3}}+\tan (-x)+\frac{{{(-x)}^{2}}+1}{P}\]                    \[g(-x)=-{{x}^{3}}-\tan x+\frac{{{x}^{2}}+1}{P}\]                    \[g(x)+g(-x)=0\]because \[g(x)\] is a odd function                    \\[\left[ {{x}^{3}}+\tan x+\frac{{{x}^{2}}+1}{P} \right]\] \[+\left[ -{{x}^{3}}-\tan x+\frac{{{x}^{2}}+1}{P} \right]=0\]                    Þ \[\frac{2({{x}^{2}}+1)}{P}=0\] Þ \[0\le \frac{{{x}^{2}}+1}{P}<1\] because \[x\in [-2,\,2]\]                    Þ \[0\le \frac{5}{P}<1\Rightarrow P>5\].


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