JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    Let \[f:R\to R\] be a function defined by \[f(x)=\frac{x-m}{x-n}\], where \[m\ne n\]. Then [UPSEAT 2001]

    A)                    f is one-one onto

    B)            f is one-one into

    C)            f is many one onto

    D)            f is many one into

    Correct Answer: B

    Solution :

               For any \[x,\,y\in R,\] we have            \[f(x)=f(y)\Rightarrow \frac{x-m}{x-n}=\frac{y-m}{y-n}\Rightarrow x=y\]            \ f is one-one.            Let aÎR such that \[f(x)=\alpha \Rightarrow \frac{x-m}{x-n}=\alpha \]Þ \[x=\frac{m-n\alpha }{1-\alpha }\]            Clearly \[x\notin R\] for \[\alpha =1\]. So, f is not onto.


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