CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2003

  • question_answer
    If \[{{I}_{n}}\int{{{(\log \,x)}^{n}}dx}\] then \[{{I}_{n}}+n\,{{I}_{n-1}}\] is equal to :

    A)  \[{{(x\,\log \,x)}^{n}}\]                                

    B)  \[x\,{{(\log \,x)}^{n}}\]

    C)  \[n\,{{(\log \,x)}^{n}}\]               

    D)  \[{{(\log \,x)}^{n-1}}\]

    Correct Answer: B

    Solution :

    Here we have                 \[{{I}_{n}}=\int{{{(\log \,x)}^{n}}dx}\] \[\therefore \]  using \[\int{(u\upsilon )\,dx=[\upsilon \,.\,\,\int{\upsilon \,dx]-\int{\left\{ \frac{du}{dx}\,.\,\int{\upsilon \,dx} \right\}dx}}}\]                 \[={{(\log \,x)}^{n}}.\,x-\int{x\,.\,n\,{{(\log \,x)}^{n-1}}\frac{1}{x}dx}\]                 \[{{I}_{n}}=x\,{{(\log \,x)}^{n}}-n\,{{I}_{n-1}}\] \[\therefore \]  \[{{I}_{n}}+n{{I}_{n-1}}=x\,{{(\log \,x)}^{n}}\]


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