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    Question

    {(21/20) + (20/21)}2 - {(21/20) -

    (20/21)}2 = ?
    A 4 Correct Answer Incorrect Answer
    B 3 Correct Answer Incorrect Answer
    C 14 Correct Answer Incorrect Answer
    D 12 Correct Answer Incorrect Answer

    Solution

    let a = 21/20 , b = 20/21  so  {(21/20) + (20/21)} 2 - {(21/20) - (20/21)} 2 we know that, (a+ b)2 - (a - b)2 = 4ab 4 x 21/20 x 20/21 = 4 ` `

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