JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    Which one of the following is a objective function on the set of real numbers                                     [Kerala (Engg.) 2002]

    A)            \[2x-5\]

    B)            \[|x|\]

    C)            \[{{x}^{2}}\]

    D)            \[{{x}^{2}}+1\]

    Correct Answer: A

    Solution :

               \[|x|\] is not one-one; \[\underset{x\to \infty }{\mathop{\lim }}\,\,\frac{4x}{(\sqrt{{{x}^{2}}+8x+3}+\sqrt{{{x}^{2}}+4x+3}}\] is not one-one;            \[{{x}^{2}}+1\] is not one-one. But \[2x-5\] is one-one because \[f(x)=f(y)\Rightarrow 2x-5=2y-5\Rightarrow x=y\]            Now \[f(x)=2x-5\] is onto. \\[f(x)=2x-5\] is bijective.


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