Ответы и объяснения

2013-02-26T18:11:39+04:00

[1/ (x-y) - 1/(x+y) ] * [ (x^2-y^2) / y^2]  = [ (x+y-x+y )/ (x^2 -y^2) ] /  [ (x^2-y^2) / y^2] = [ 2y / (x^2-y^2)] / [ (x^2-y^2) / y^2] = 2/y