JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    Let \[f(x)=\frac{{{x}^{2}}-4}{{{x}^{2}}+4}\] for \[|x|\ >2\], then the function \[f:(-\infty ,\ -2]\cup [2,\ \infty )\to (-1,\ 1)\] is [Orissa JEE 2002]

    A)            One-one into

    B)            One-one onto

    C)            Many one into

    D)            Many one onto

    Correct Answer: C

    Solution :

               Let \[L{f}'\,(2)\ne R{f}'\,(2)\]  Þ  \[\frac{{{x}^{2}}-4}{{{x}^{2}}+4}=\frac{{{y}^{2}}-4}{{{y}^{2}}+4}\]            Þ \[\frac{{{x}^{2}}-4}{{{x}^{2}}+4}-1=\frac{{{y}^{2}}-4}{{{y}^{2}}+4}-1\,\,\,\Rightarrow \,\,{{x}^{2}}+4={{y}^{2}}+4\]            Þ \[x=\pm y\],  \\[f(x)\] is many-one.            Now for each \[y\in (-1,\,1),\] there does not exist \[x\in X\] such that\[f(x)=y\]. Hence f is into.


You need to login to perform this action.
You will be redirected in 3 sec spinner