8th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions & Identities

  • question_answer
    The product of \[\left( x-\frac{1}{x} \right)\left( x+\frac{1}{x} \right)\left( {{x}^{2}}+\frac{1}{{{x}^{2}}} \right)\left( {{x}^{4}}+\frac{1}{{{x}^{4}}} \right)\] is

    A)  \[\left( {{x}^{8}}-\frac{1}{{{x}^{8}}} \right)\]                       

    B)  \[\left( {{x}^{4}}-\frac{1}{{{x}^{4}}} \right)\]      

    C)  \[\left( {{x}^{2}}-\frac{1}{{{x}^{2}}} \right)\]           

    D)  \[\left( {{x}^{8}}+\frac{1}{{{x}^{8}}} \right)\]

    Correct Answer: A

    Solution :

    (a): \[\left( x-\frac{1}{x} \right)\left( x+\frac{1}{x} \right)={{x}^{2}}-{{\left( \frac{1}{x} \right)}^{2}}={{x}^{2}}-\frac{1}{{{x}^{2}}}\] Then, \[\left( {{x}^{2}}-\frac{1}{{{x}^{2}}} \right)\left( {{x}^{2}}+\frac{1}{{{x}^{2}}} \right)={{x}^{4}}-\frac{1}{{{x}^{4}}}\]. Then, \[\left( {{x}^{4}}-\frac{1}{{{x}^{4}}} \right)\times \left( {{x}^{4}}+\frac{1}{{{x}^{4}}} \right)={{x}^{8}}-\frac{1}{{{x}^{8}}}\]


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