(1/x-y - 1/x+y) * (x - 3x +y/4)
1) 1/x-y - 1/x+y (приводим к общему знаменателю) = (x+y) - (x-y)/(x+y)(x-y)=(открываем скобки в числителе) x+y-x+y/(x+y)(x-y) = 2y/(x+y)(x-y)
2) x - 3x +y/4 = 4x - (3x+y)/4= 4x -3x -y/4 = x-y/4
3) 2y/(x+y)(x-y) * x-y/4 (сокращаем x-y и 2y и 4)= y/2(x+y)