JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Expansion of binomial theorem

  • question_answer
    \[{{(1+x)}^{n}}-nx-1\] divisible (where \[n\in N\])

    A) by \[2x\]

    B) by \[{{x}^{2}}\]

    C) by \[2{{x}^{3}}\]

    D) All of these

    Correct Answer: B

    Solution :

    \[{{(1+x)}^{n}}=1+nx+\frac{n(n-1)}{1.2}{{x}^{2}}+\frac{n(n-1)(n-2)}{1.2.3}{{x}^{3}}+....\] \ \[{{(1+x)}^{n}}-nx-1={{x}^{2}}\left[ \frac{n(n-1)}{1.2}+\frac{n(n-1)(n-2)}{1.2.3}x+.... \right]\] From above it is clear that \[{{(1+x)}^{n}}-nx-1\]is divisible by x2.


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