Find the value of \(x-y\over1 +xy\) if \({x+1\over x-1}={a\over b}\) and \({1-y\over1+y} ={b \over a}\)
1
a2 - b2
2
\({2ab\over a^2 -b^2}\)
3
a + b
4
(a + b)2
Find the value of \(x-y\over1 +xy\) if \({x+1\over x-1}={a\over b}\) and \({1-y\over1+y} ={b \over a}\)