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    • 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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