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

  • question_answer
    If \[\left( \mathbf{a}+\mathbf{b} \right)=\mathbf{2}\] and \[\left( \mathbf{a}-\mathbf{b} \right)=\mathbf{10}.\] Find the value of \[\left( {{a}^{2}}+{{b}^{2}} \right)=10.\]

    A)  40                               

    B)  52   

    C)  38                               

    D)  42

    Correct Answer: B

    Solution :

    (b): \[{{(a+b)}^{2}}{{(a-b)}^{2}}={{2}^{2}}+{{10}^{2}}\] \[\Rightarrow 2\left\{ {{a}^{2}}+{{b}^{2}} \right\}=104.\] \[\Rightarrow {{a}^{2}}+{{b}^{2}}=52.\]


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