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9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    If \[x+\frac{1}{x}=a+b\] and \[x-\frac{1}{x}=a-b\], which of the following is true?

    A) \[ab=1\]           

    B)        \[a=b\] 

    C)        \[ab=2\]           

    D)        \[a+b=0\]

    Correct Answer: A

    Solution :

    \[x+\frac{1}{x}=a+b\]and \[x-\frac{1}{x}=a-b\] \[\Rightarrow \]\[2x-2a\Rightarrow x=a\] Similarly, \[\frac{2}{x}=2b\Rightarrow \frac{1}{x}=b\] \[\therefore \]      \[x+\frac{1}{x}=a\times b\Rightarrow ab=1\]


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