JEE Main & Advanced Sample Paper JEE Main Sample Paper-39

  • question_answer
    DIRECTION: Each of these questions contains two statements: Statement-1 (Assertion) and Statement-2 (Reason). Choose the correct answer (Only one option is correct) from the following -
    Statement-1: Integral part of\[{{\left( \sqrt{3}+1 \right)}^{2n+1}}\] is even where \[n\in I.\]
    Statement-2: Integral part of any integral power of the expression of the form of \[p+\sqrt{q}\]is even.

    A)  Statement-1 is false, Statement-2 is true.

    B)  Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.

    C)  Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.

    D)  Statement-1 is true, Statement-2 is false.

    Correct Answer: D

    Solution :

     \[{{(\sqrt{3}+1)}^{2n+1}}\] \[{{=}^{2n+1}}{{C}_{0}}{{(\sqrt{3})}^{2n+1}}{{+}^{2n+1}}{{C}_{1}}{{(\sqrt{3})}^{2n}}\] \[{{+}^{2n+1}}{{C}_{2}}{{(\sqrt{3})}^{2n-1}}+......{{+}^{2n+1}}{{C}_{2n+1}}...\]            (1) \[{{(\sqrt{3}-1)}^{2n+1}}{{=}^{2n+1}}{{C}_{0}}{{(\sqrt{3})}^{2n+1}}{{-}^{2n+1}}{{C}_{1}}{{(\sqrt{3})}^{2n}}\] \[{{+}^{2n+1}}{{C}_{2}}{{(\sqrt{3})}^{2n-1}}+{{.....}^{2n+1}}{{C}_{2n+1}}\]                   ..(2) Subtracting (2) from (1) \[{{(\sqrt{3}+1)}^{2n+1}}-{{(\sqrt{3}-1)}^{2n+1}}\] \[=2{{(}^{2n+1}}{{C}_{1}}{{(\sqrt{3})}^{2n}}+{{C}_{3}}{{(\sqrt{3})}^{2n-1}}+...)\] \[I+f-{{f}_{1}}=\] even integer Now, \[0<f<1\Rightarrow -1<f-{{f}_{1}}<1\Rightarrow f-{{f}_{1}}=0\] \[0<{{f}_{1}}<1.\]so 1 =even integer


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