JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    The function \[f:R\to R\] defined by \[f(x)=(x-1)\] \[(x-2)(x-3)\]  is [Roorkee 1999]

    A)                    One-one but not onto

    B)            Onto but not one-one

    C)            Both one-one and onto

    D)            Neither one-one nor onto

    Correct Answer: B

    Solution :

               We have \[f(x)=(x-1)(x-2)(x-3)\]                    and \[f(1)=f(2)=f(3)=0\] Þ \[f(x)\] is not one-one.            For each x\[y\in R\], there exists \[x\in R\] such that \[f(x)=y\]. Therefore f is onto. Hence \[f:R\to R\] is onto but not one-one.


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