10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    H.C.F. of \[{{x}^{3}}-1\] and \[{{x}^{4}}+{{x}^{2}}+1\] will be

    A) \[x-1\]                                 

    B) \[{{x}^{2}}+x+1\]  

    C) \[{{x}^{2}}-x+1\]             

    D)        \[{{x}^{2}}-x-1\]

    Correct Answer: B

    Solution :

                    \[{{x}^{3}}-1={{x}^{3}}-{{1}^{3}}\]                           \[=(x-1)({{x}^{2}}+x+1)\]       \[{{x}^{4}}+{{x}^{2}}+1=({{x}^{4}}+2{{x}^{2}}+1)-{{x}^{2}}\]                           \[={{({{x}^{2}}+1)}^{2}}-{{(x)}^{2}}\]                           \[=({{x}^{2}}+1+x)({{x}^{2}}+1-x)\]                           \[=({{x}^{2}}+x+1)({{x}^{2}}-x+1)\] Hence, \[H.C.F.\] of \[{{x}^{3}}-1\] and \[{{x}^{4}}+{{x}^{2}}+1\] is\[{{x}^{2}}+x+1\].


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