JEE Main & Advanced AIEEE Solved Paper-2006

  • question_answer
    The value of \[\int_{I}^{a}{[x]\,f'\,(x)\,dx,\,\,a>1,}\] where\[[x]\] denotes  the  greatest  integer  not exceeding \[x,\]is       AIEEE  Solved  Paper-2006

    A) \[[a]f(a)-\{f(1)+f(2)+....+f([a])\}\]

    B) \[[a]f([a])-\{f(1)+f(2)+....+f(a)\}\]

    C) \[af([a])-\{f(1)+f(2)+....+f(a)\}\]

    D) \[af(a)-\{f(1)+f(2)+....+f([a])\}\]

    Correct Answer: A

    Solution :

    Since, \[\int_{1}^{a}{[x]f'}(x)dx=\int_{1}^{2}{f'}(x)dx\] \[+\int_{2}^{3}{2f'(x)+......+\int_{[a]}^{a}{[a]f'(x)dx}}\] \[=[f(x)]_{1}^{2}+2[f(x)]_{2}^{3}+.....+[a][f(x)]_{[a]}^{a}\] \[=[a]f(a)-\{f(1)+f(2)+....+f([a])\}\]


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