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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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