9th Class Mathematics Number System and its Operations Question Bank Number System

  • question_answer
    If \[m=\sqrt{3+\sqrt{3+\sqrt{3+.....}}}\] \[n=\sqrt{3-\sqrt{3-\sqrt{3-.........}}}\] Then among the following the relation between m and n holds is

    A)  \[m-n+1=0\]                

    B)  \[~m+n-1=0\]

    C)  \[m+n+1=0\]           

    D)  \[m-n-1=0\]

    Correct Answer: D

    Solution :

    (d): \[m=\sqrt{3+\sqrt{3+\sqrt{3+......}}}\] on squaring both sides, \[{{m}^{2}}=3+m\Rightarrow {{m}^{2}}-m=3\]         ?..(i) Again, \[n=\sqrt{3-\sqrt{3-\sqrt{3-.....}}}\] On squaring both sides, \[{{n}^{2}}=3-n\] \[\Rightarrow {{n}^{2}}+n=3\]                     ????(ii) \[\therefore {{m}^{2}}-m={{n}^{2}}+n\Rightarrow \left( {{m}^{2}}-{{n}^{2}} \right)=m+n\] \[\Rightarrow \left( m+n \right)\left( m-n \right)-\left( m+n \right)=0\] \[\Rightarrow \left( m+n \right)\left( m-n-1 \right)=0\]


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