JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Substitution

  • question_answer
    \[\int_{{}}^{{}}{\frac{1}{{{[{{(x-1)}^{3}}{{(x+2)}^{5}}]}^{1/4}}}\ dx}\] is equal to

    A)            \[\frac{4}{3}{{\left( \frac{x-1}{x+2} \right)}^{1/4}}+c\]

    B)            \[\frac{4}{3}{{\left( \frac{x+2}{x-1} \right)}^{1/4}}+c\]

    C)            \[\frac{1}{3}{{\left( \frac{x-1}{x+2} \right)}^{1/4}}+c\]

    D)            \[\frac{1}{3}{{\left( \frac{x+2}{x-1} \right)}^{1/4}}+c\]

    Correct Answer: A

    Solution :

               \[\int_{{}}^{{}}{\frac{1}{{{[{{(x-1)}^{3}}{{(x+2)}^{5}}]}^{1/4}}}}\,dx=\int_{{}}^{{}}{\frac{1}{{{\left( \frac{x-1}{x+2} \right)}^{3/4}}{{(x+2)}^{2}}}}\,dx\]            \[=\frac{1}{3}\int_{{}}^{{}}{\frac{1}{{{t}^{3/4}}}\,dt}\],            \[\left\{ \because \,\,\,\frac{x-1}{x+2}=t\Rightarrow \frac{3}{{{(x+2)}^{2}}}\,dx=dt \right\}\]            \[=\frac{1}{3}\left( \frac{{{t}^{1/4}}}{1/4} \right)+c=\frac{4}{3}{{t}^{1/4}}+c=\frac{4}{3}{{\left( \frac{x-1}{x+2} \right)}^{1/4}}+c\].


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