Inequalities

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 324
Joined: Thu Dec 24, 2009 6:29 am
Thanked: 17 times
Followed by:1 members

Inequalities

by rahul.s » Mon Jan 25, 2010 11:46 pm
Is x > y^2?

1) x > y + 5
2) x^2 - y^2 = 0

OA: C

Tried plugging in numbers, but I guess I couldn't find the apt ones.

User avatar
Legendary Member
Posts: 1275
Joined: Thu Sep 21, 2006 11:13 pm
Location: Arabian Sea
Thanked: 125 times
Followed by:2 members

by ajith » Tue Jan 26, 2010 12:33 am
rahul.s wrote:Is x > y^2?

1) x > y + 5
2) x^2 - y^2 = 0

OA: C

Tried plugging in numbers, but I guess I couldn't find the apt ones.
1. Alone is not sufficient [ y = -3 , then x = 2 then x<y^2 if y =0 and x =5 the x>y^2]

2. alone is not sufficient [x^2 = y^2 now x can be greater or less than y^2]

Now combining 1 and 2

from 2

x= +/- y

now, since if x = y if we substitute the same in 1. we get y>y+5 which is doesn't make sense

so x = -y ---- (3)

-y> y+5

-2y>5

y<-5/2 ---- (4)

Since |y| = |x| and|y|> 5/2 x < y^2

hence C
Always borrow money from a pessimist, he doesn't expect to be paid back.

Master | Next Rank: 500 Posts
Posts: 324
Joined: Thu Dec 24, 2009 6:29 am
Thanked: 17 times
Followed by:1 members

by rahul.s » Tue Jan 26, 2010 1:55 am
i tried combining the 2 statements, but i guess i was just frustrated by the end of it. i didn't think of substituting x = -y in the 1st statement. will keep that in mind. thanks.