SSC Sample Paper SSC-CGL TIER - I Sample Test Paper-9

  • question_answer
    \[x+y\] is a factor of\[{{x}^{n}}+{{y}^{n}}\] for:

    A) All natural numbers n

    B) All odd natural numbers n

    C) All even natural numbers n

    D) None of the above

    Correct Answer: B

    Solution :

    Let \[(x+y)\]is a factor of \[{{x}^{n}}+{{y}^{n}}.\] Then, \[x=-y\] will satisfy\[{{x}^{n}}+{{y}^{n}}\], \[\forall \]odd\[n\in N\]. \[\forall \,\,even\,\,n\in N.\,\,{{x}^{n}}+{{y}^{n}}\ne 0\] Hence \[{{x}^{n}}+{{y}^{n}}.\] has a factor \[(x+y)\] \[\forall \]odd\[n\in N\]. Alternate method:- \[\therefore \]  \[(x+y)\] is a factor of \[{{x}^{n}}+{{y}^{n}}.\] \[\Rightarrow \,\,\,\,\,\,{{x}^{n}}+{{y}^{n}}=0\Rightarrow {{x}^{n}}+{{y}^{n}}.\] \[\Rightarrow \,\,\,\,\,\,{{x}^{n}}={{\left( -y \right)}^{n}}\,\,for\,\,all\,\,odd\,\,n.\] \[\Rightarrow \,x+y=0\]


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