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    Question

    If, p³ + q³= 485 and (p + q = 5), then find the value

    of [(1/p) + (1/q)]
    A - (2/19) Correct Answer Incorrect Answer
    B - (15/23) Correct Answer Incorrect Answer
    C - (5/24) Correct Answer Incorrect Answer
    D - (7/24) Correct Answer Incorrect Answer

    Solution

    ATQ, We know that, (a + b)³= a³ + b³ + 3ab × (a + b) So, (p + q)³= p³ + p³ + 3pq × (p + q) Or, 5³= 485 + 3 × pq × 5 Or, 15pq = 125 - 485 Or, pq = - (360/15) So, pq = - 24 (1/p) + (1/q) = (p + q)/pq = 5 ÷ ( - 24) = - (5/24)

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