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7th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions

  • question_answer
    If \[5x-\frac{1}{2x}=6,\] then the value of \[25{{x}^{2}}+\frac{1}{4{{x}^{2}}}\] is:

    A)  31                               

    B)  37

    C)  39                               

    D)  41

    Correct Answer: D

    Solution :

    (d) \[36={{\left( 5x-\frac{1}{2x} \right)}^{2}}=25{{x}^{2}}+\frac{1}{4{{x}^{2}}}-2.5x\frac{1}{2x}\] \[=\left( 25{{x}^{2}}+\frac{1}{4{{x}^{2}}} \right)-5\] \[\therefore \,\,\left( 25{{x}^{2}}+\frac{1}{4{{x}^{2}}} \right)=36+5=41\]


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