RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    Function\[f(x)=1+\alpha x,\alpha \ne 0\]is equal to its reciprocal, then the value of\[\alpha \]is

    A)  \[-2\]               

    B)  \[-1\]

    C)  \[1\]                

    D)  2

    Correct Answer: B

    Solution :

     Given, \[f(x)=1+\alpha x,\alpha \ne 0\] Let \[1+ax=y\] \[\Rightarrow \] \[\alpha x=y-1\] \[\Rightarrow \] \[x=\frac{y-1}{\alpha }=f(y)\] Since,\[f(x)\]is equal to its reciprocal \[\therefore \] \[\frac{y-1}{\alpha }=1+\alpha y\] \[\Rightarrow \] \[\frac{1}{\alpha }=\alpha \] and \[-\frac{1}{\alpha }=1\] \[\Rightarrow \] \[{{\alpha }^{2}}=1\] and \[\alpha =-1\] \[\Rightarrow \] \[\alpha =\pm 1\] and \[\alpha =-1\] \[\Rightarrow \] \[\alpha =-1\]


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