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If x is not equal to |y|, is \(\frac{x-y}{x+y} > \frac{x+y}{x-y}\)?
(1) \(x > y^2\)
(2) \(x^2>y>0\)
Are You Up For the Challenge: 700 Level Questions Is \(\frac{x-y}{x+y} > \frac{x+y}{x-y}\)?
(I) \(x>y^2\)
This gives, \(x>y \) or \(x-y>0\). But what about \(x+y\)? What if \(y=-4\) and \(x=4\). That would give \(x+y=0\) And the L.H.S would become not defined. So, this alone is
insufficient.
(II) \(x^2>y>0\)
This can lead to three possibilities,
Case (A) \(x<y (x=2,y=3,x^2=4)\)
In this case, is \(\frac{x-y}{x+y} > \frac{x+y}{x-y}\) = \(\frac{2-3}{2+3} > \frac{2+3}{2-3}\) = \(\frac{-1}{5} > \frac{-5}{1}\). So, Yes! \(\frac{x-y}{x+y} > \frac{x+y}{x-y} \)
holds.
Case (B) \(x=y (x=2,y=2)\)
For this x-y = 2-2= 0. This makes R.H.S not defined. Not possible.
Case (C)\(x>y (x=3,y=2)\)
\(\frac{x-y}{x+y} > \frac{x+y}{x-y}\) = \(\frac{3-2}{3+2} > \frac{3+2}{3-2}\) = \(\frac{1}{5} > \frac{5}{1}\)? No! \(\frac{x-y}{x+y} > \frac{x+y}{x-y}\)
does not hold.
Thus,
insufficient, since cases (A) and (C) give contradictory answers.
(I) + (II) = \(x>y\)
In that case (C) gives a definite unique answer=No. Thus, both are sufficient together.
So, answer is option
(C).