If x + y + z = 5, x2 + y2 + z2 = 21 and y2 = zx, then the value of y is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. .
(x + y + z)2 = x2 + y2 + z2 + 2(xy + yz + zx)
⇒ (5)2 = 21 + 2(xy + yz + zx)
⇒ 2(xy + yz + zx) = 4
⇒ xy + yz + y2 = 2 [y2 = zx]
⇒ y(x + z + y) = 2
⇒ y(5) = 2
⇒ y =