KVPY2020MathematicsBasics of Mathematics
Let x ,   y be real numbers such that x > 2 y > 0 and 2 log x - 2 y = log x + log y . Then the possible value s of x y
Options
- Ais 1 only
- Bare 1 and 4
- Cis 4 only
- Dis 8 only
Correct answer
C. is 4 only
Step-by-step solution
log x − 2 y 2 = log x y ⇒ x − 2 y 2 = x y ⇒ x − 2 y y 2 = x y ⇒ x y 2 − 5 x y + 4 = 0 ⇒ x y = 1 , 4 ⇒ x y = 4   as   x y > 2