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Question
If 4x2 + y2 = a and xy = b, find the value of 2x + y.
Sum
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Solution
xy = b ….(i)
4x2 + y2 = a ….(ii)
Now, (2x + y)2 = (2x)2 + 4xy + y2
= 4x2 + y2 + 4xy
= a + 4b ….[From (i) and (ii)]
⇒ 2x + y = `+- sqrt( a + 4b)`
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