-
loveusonu
- Master | Next Rank: 500 Posts
- Posts: 278
- Joined: Sun Jul 26, 2009 1:17 pm
- Location: Bangalore,India
- Thanked: 17 times
Is x/3 + 3/x >2
(1) x<2
(2) x>1
[spoiler]OA: C ; IMO B[/spoiler]
Here is my solution to reach B:
x/3 + 3/x >2
Cross multiplying the left hand side, we get
(x^2 + 9) / 3x > 2
we know x^2 will always be positive and 9 is also positive, so numerator will always be positive and greater than 9 for sure.
Now if x is -ve then eqn is false as denominator will be -ve.
And if x is +ve then eqn will be true as denominator will be +ve and offcourse x^2 + 9 will be many times greater.
In short question is asking, is X -ve or +ve ?
(1) x<2 ---> x can be positive or it can be -ve as well.(checked for max value 2 as well and answer is coming YES too)
(2) x>1 --> This says X is always +ve , meaning eqn is true.
Hence went with B.
Where am I going wrong.
(1) x<2
(2) x>1
[spoiler]OA: C ; IMO B[/spoiler]
Here is my solution to reach B:
x/3 + 3/x >2
Cross multiplying the left hand side, we get
(x^2 + 9) / 3x > 2
we know x^2 will always be positive and 9 is also positive, so numerator will always be positive and greater than 9 for sure.
Now if x is -ve then eqn is false as denominator will be -ve.
And if x is +ve then eqn will be true as denominator will be +ve and offcourse x^2 + 9 will be many times greater.
In short question is asking, is X -ve or +ve ?
(1) x<2 ---> x can be positive or it can be -ve as well.(checked for max value 2 as well and answer is coming YES too)
(2) x>1 --> This says X is always +ve , meaning eqn is true.
Hence went with B.
Where am I going wrong.
Sonu
--------
When you want something desperately, the whole Universe conspires in helping to give it to you - The Alchemist
--------
When you want something desperately, the whole Universe conspires in helping to give it to you - The Alchemist
