J & K CET Engineering J and K - CET Engineering Solved Paper-2012

  • question_answer
    If \[f(x)={{(1+x)}^{n}},\] then the value of \[f(0)+f'(0)+\frac{f'\,'(0)}{2!}+.....+\frac{{{f}^{(n)}}(0)}{n!}\] is equal  to

    A)  \[{{2}^{n-1}}\]

    B)  \[2\,n\]

    C)  \[n\]

    D)  \[{{2}^{n}}\]

    Correct Answer: D

    Solution :

    Given,  \[f(x)={{(1+x)}^{n}}\] On differentiating w. r. t. x, we get \[f'(x)=n{{(1+x)}^{n-1}}\] Again, differentiating, we get \[f''(x)=n(n-1)\,{{(1+x)}^{n-2}}\] \[\therefore \]   \[{{f}^{n}}(x)=n(n-1).....\,\,\,3.2.1=n!\] \[\therefore \]  \[f(0)+f'(0)+\frac{f''(0)}{2!}+....\frac{{{f}^{n}}(0)}{n!}\] \[=1+n+\frac{n(n-1)}{2!}+....+\frac{n!}{n!}\] \[{{=}^{n}}{{C}_{0}}{{+}^{n}}{{C}_{1}}{{+}^{n}}{{C}_{2}}+...{{+}^{n}}{{C}_{n}}\] \[={{2}^{n}}\]


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