JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    The term independent of x in expansion of \[{{\left( \frac{x+1}{{{x}^{2/3}}-{{x}^{1/3}}+1}-\frac{x}{x-{{x}^{1/2}}} \right)}^{10}}\]is:     AIEEE Solevd Paper-2013

    A) 4             

    B)                        120                        

    C)        210                        

    D)        310

    Correct Answer: C

    Solution :

    \[{{\left[ \frac{x+1}{{{x}^{2/3}}-{{x}^{1/3}}+1}-\frac{x-1}{x-{{x}^{1/2}}} \right]}^{10}}\] \[\Rightarrow \]\[{{\left[ ({{x}^{1/3}}+1)-(1+{{x}^{-1/2}}) \right]}^{10}}\] \[\Rightarrow \]\[{{[{{x}^{1/3}}-{{x}^{-1/2}}]}^{10}}\] \[\Rightarrow \]\[{{T}_{r+1}}{{=}^{10}}{{C}_{r}}{{({{x}^{1/3}})}^{10-r}}{{(-{{x}^{-1/2}})}^{r}}\] \[{{T}_{r+1}}{{=}^{10}}{{C}_{r}}{{x}^{\frac{10-r}{3}\frac{-r}{2}{{(-1)}^{r}}}}\] \[{{T}_{r+1}}{{=}^{10}}{{C}_{r}}{{x}^{\frac{20-5r}{6}{{(-1)}^{r}}}}\] \[\Rightarrow \]\[20-5r=0\] \[\Rightarrow \]\[r=4\] \[\Rightarrow \] \[{{T}_{5}}=10{{C}_{4}}=210\]


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