Quote:
Statement 1
\(x+y>\frac{1}{x-y}\)
\(\frac{x^2-y^2-1}{x-y}\)>0
When x^2-y^2>1, x>y
and when x^2-y^2<1, x<y
Insufficient
Statement 2
\(\frac{1}{x}<\frac{1}{y}\)
\(\frac{x-y}{xy}>0\)
When x and y has same signs, x>y
When x and y have opposite signs, x<y
Insufficient
Combining both equations
From equation 1
\(x+y>\frac{1}{x-y}\)
x+y>
\(\frac{xy}{x-y}\)*\(\frac{1}{xy}\)
From statement 2, we can say that highlighted portion is positive. Hence we can cross-multiply it without the change of inequality sign.
We get, \(\frac{x^2-y^2-1}{xy}\)>0
When x and y has same sign x^2-y^2-1 is positive. Hence when x and y are both positive, then x>y. But when x and y are both negative, x can be greater or smaller than y. We don't need to analyse further, as we get our answer.
Option E
PreiteeRanjan wrote:
AvidDreamer09 wrote:
Is x>y?
1) \(x+y>\frac{1}{x-y}\)
If x=3 and y=2
\(3+2> \frac{1}{(3-2)}\) -> 5>1 -> x>y Yes!
If x=-2 and y=3
\(-2+3>\frac{1}{(-2-3)}\) -> 1>1/-5 No still holds true y>x
Not sufficient
2) \(1/x<1/y\)
If x=3 and y=2
\(1/3<1/2 -> x>y\) Yes!
If x=-2 and y=3
\(-1/2<1/3\) No as y>x holds true
not sufficient
from 1 and 2: We can conclude x>y only if we know xy>0 or we would get yes and No. Not sufficient E
PS: does anyone know how to use algebra approach for this questions?
any genereic approach for such kind of qns kindly post here.