JEE Main & Advanced JEE Main Paper (Held On 9 April 2016)

  • question_answer
    For \[x\in R,x\ne 0,x\ne 1,\]let\[{{f}_{0}}(x)=\frac{1}{1-x}\]and\[{{f}_{n+1}}(x)={{f}_{0}}(f{{(}_{n}}(X)),\]n = 0, 1, 2, ........ Then the value of \[{{f}_{100}}(3)+{{f}_{1}}\left( \frac{2}{3} \right)+{{f}_{2}}\left( \frac{3}{2} \right)\]is equal to:   JEE Main Online Paper (Held On 09 April 2016)

    A) \[\frac{4}{3}\]   

    B) \[\frac{1}{3}\]

    C) \[\frac{5}{3}\]                                   

    D) \[\frac{8}{3}\]

    Correct Answer: C

    Solution :

                    \[{{f}_{0}}(x)=\frac{1}{1-x}\]                 \[{{f}_{1}}(x)={{f}_{0}}({{f}_{0}}(x))=\frac{1}{1-{{f}_{0}}(x)};{{f}_{0}}(x)\ne 1\] \[=\frac{1}{1-\frac{1}{1-x}}x\ne 0\] \[=\frac{1-x}{-x}\] \[{{f}_{2}}(x)={{f}_{0}}({{f}_{1}}(x))=\frac{1}{1-{{f}_{1}}(x)};{{f}_{1}}(x)\ne 1\] \[=\frac{1}{1+\frac{1-x}{x}}=x\] similarly \[{{f}_{3}}(x)={{f}_{0}}(x)\]                 \[{{f}_{4}}(x)={{f}_{1}}(x)\]??? \[{{f}_{100}}(3)+{{f}_{1}}\left( \frac{2}{3} \right)+{{f}_{2}}\left( \frac{3}{2} \right)={{f}_{1}}(3)+{{f}_{1}}\left( \frac{2}{3} \right)+\frac{3}{2}\] \[=1-\frac{1}{3}+1-\frac{3}{2}+\frac{3}{2}=\frac{5}{3}\]


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