If x + y = √13 and x - y = √11, then the value of xy (x2 + y2 ) is:
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Correct answer: B
Explanation
The correct answer is Option 2 i.e. 6.
(x + y)2 = 13 .....(1)
(x - y)2 = 11 .....(2)
Adding (1) and (2), 2(x2 + y2) = 24
⇒ x2 + y2 = 12
Subtract (2) from (1), 4xy = 2
xy = 0.5
So, xy(x2 + y2) = 0.5 × 12 = 6