Question

If 4x² + y² = a and xy = b, find the value of 2x + y.

Answer 1

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)`