JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Evening)

  • question_answer
    If\[\int_{{}}^{{}}{\frac{x+1}{\sqrt{2x-1}}}dx=f(x)\sqrt{2x-1}+C,\]where C is a constant of integration, then f(x) is equal to [JEE  Main Online Paper (Held on 11-jan-2019 Evening)]

    A) \[\frac{1}{3}(x+1)\]                              

    B) \[\frac{1}{3}(x+4)\]

    C) \[\frac{2}{3}(x+2)\]                  

    D)   \[\frac{2}{3}(x-4)\]

    Correct Answer: B

    Solution :

    Let\[I=\int_{{}}^{{}}{\frac{x+1}{\sqrt{2x-1}}}dx\] Put\[2x-1={{t}^{2}}\Rightarrow 2dx=2t\,dt\] \[\therefore \]\[I=\int_{{}}^{{}}{\frac{\frac{{{t}^{2}}+1}{2}+1}{t}t\,dt}=\frac{1}{2}\int_{{}}^{{}}{({{t}^{2}}+3)}dt\] \[=\frac{1}{2}\left( \frac{{{t}^{3}}}{3}+3t \right)+C=\frac{t}{6}({{t}^{2}}+9)+C\] \[=\frac{\sqrt{2x-1}}{6}(2x-1+9)+C=\sqrt{2x-1}\left( \frac{x+4}{3} \right)+C\] \[\therefore \]\[f(x)=\frac{x+4}{3}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner