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    Question

    If p = 50 - q - r and pq + r(q + p) = 816 then find the

    value of (p2 + q2 + r2) .
    A 868 Correct Answer Incorrect Answer
    B 832 Correct Answer Incorrect Answer
    C 844 Correct Answer Incorrect Answer
    D 852 Correct Answer Incorrect Answer

    Solution

    We have, p = 50 - q - r

    So, p + q + r = 50

    And, pq + r(q + p) = 816

    Or, pq + qr + pr = 816

    Using, (p + q + r) 2 = p2 + q2 + r2 + 2(pq + qr + pr)

    So, 502 = (p2 + q2 + r2) + 2 X 816

    Or, p2 + q2 + r2 = 2,500 - 1,632

    So, p2 + q2 + r2 = 868

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