Question

    If p = 28 - q - r and pq + r(p + q) = 231, then find the

    value of (p² + q² + r²).
    A 299 Correct Answer Incorrect Answer
    B 315 Correct Answer Incorrect Answer
    C 322 Correct Answer Incorrect Answer
    D 328 Correct Answer Incorrect Answer

    Solution

    We have, p = 28 - q - r
    So, p + q + r = 28
    And, pq + r(p + q) = 231
    Or, pq + qr + pr = 231
    Using, (p + q + r)² = p² + q² + r² + 2(pq + qr + pr)
    28² = (p² + q² + r²) + 2 × 231
    784 = (p² + q² + r²) + 462
    p² + q² + r² = 322

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