BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    Range of the function \[f(x)=\frac{x}{1+{{x}^{2}}}\]is

    A)  \[(-\infty ,\infty )\]                        

    B)         \[[-1,1]\]                            

    C)         \[\left[ -\frac{1}{2},\frac{1}{2} \right]\]                

    D)         \[[-\sqrt{2},\sqrt{2}]\]

    Correct Answer: C

    Solution :

    Let \[y=\frac{x}{1+{{x}^{2}}}\] \[\Rightarrow \]               \[{{x}^{2}}y-x+y=0\] For \[x\]to be real, \[1-4{{y}^{2}}\ge 0\] \[\Rightarrow \]\[(1-2y)(1+2y)\ge 0\] \[\Rightarrow \]\[\left( \frac{1}{2}-y \right)\left( \frac{1}{2}+y \right)\ge 0\] \[\Rightarrow \]\[-\frac{1}{2}\le y\le \frac{1}{2}\] \[\therefore \]  \[y=f(x)\in \left[ -\frac{1}{2},\frac{1}{2} \right]\]


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