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9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
      If \[\mathbf{x+}\frac{\mathbf{1}}{\mathbf{x}}\mathbf{=3}\], then the value of \[{{\mathbf{x}}^{\mathbf{4}}}+\frac{1}{{{\mathbf{x}}^{\mathbf{4}}}}\]is

    A)  56                   

    B)  74            

    C)  47       

    D)  60

    Correct Answer: C

    Solution :

    (c): Since \[\left( x+\frac{1}{x} \right)=3,\], then \[{{x}^{2}}+\frac{1}{{{x}^{2}}}=7\,\,\,\,\Rightarrow {{x}^{4}}+\frac{1}{{{x}^{4}}}=47.\]                      


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