JEE Main & Advanced Sample Paper JEE Main - Mock Test - 39

  • question_answer
    If\[\int{\frac{dt}{{{\left( 1+\sqrt{t} \right)}^{8}}}}=\frac{-1}{3{{\left( 1+\sqrt{t} \right)}^{{{p}_{1}}}}}+\frac{2}{7{{\left( 1+\sqrt{t} \right)}^{{{p}_{2}}}}}+C,\] where C is constant of integration, then \[{{p}_{1}}{{p}_{2}}=\]

    A) \[10\]                    

    B)        \[21\]                    

    C) \[36\]                    

    D)        \[42\]

    Correct Answer: D

    Solution :

    [d] Put \[t={{y}^{2}}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,I=\int{\frac{2ydy}{{{(1+y)}^{8}}}}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\int{\frac{(2y+2)-2}{{{(1+y)}^{8}}}}dy\]             \[=2\left[ \int{\frac{1}{{{(1+y)}^{8}}}-\frac{1}{{{(1+y)}^{7}}}dy} \right]\]             \[=\frac{2}{7{{(1+y)}^{7}}}-\frac{1}{3{{(1+y)}^{6}}}\]             \[=\frac{2}{7{{\left( 1+\sqrt{t} \right)}^{7}}}-\frac{1}{3{{\left( 1+\sqrt{t} \right)}^{6}}}\] \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{p}_{1}}=6,\,\,{{p}_{2}}=7\]


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