If |x| < 1, |y| < 1 and x $\neq$ y, then the sum to infinity of the following series (x + y) + (x2 + xy + y2) + (x3 + x2y + xy2 + y3) + ..... is :
(1) $x+y+xy\over(1-x)(1-y)$
(2) $x+y-xy\over(1-x)(1-y)$
(3) $x+y-xy\over(1-x)(1+y)$
(4) $x+y+xy\over(1+x)(1+y)$