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    Question

    If x + y = 2 and 1/x + 1/y = 18/15, then find the value

    of (x3 + y3)?
    A -2 Correct Answer Incorrect Answer
    B -1 Correct Answer Incorrect Answer
    C 2 Correct Answer Incorrect Answer
    D 3 Correct Answer Incorrect Answer

    Solution

    Given that, x + y = 2 and 1/x + 1/y = 18/15 Using, 1/x + 1/y = 18/15 (x + y)/xy = 18/15 2/xy = 18/15 Therefore, xy =  15/9 Now, by using formula x3 + y3 = (x + y) [(x + y)2 – 3xy]            = 2 (4 – 3 × 15/9)            = 2 (4 – 5)            = -2

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