Сократите дробь:
1) (x^2-y^2) / (y^3-x^3)

(x^2-y^2) / (y^3-x^3) = (x+y)(x-y) / (y-x) (y^2+xy+x^2) = -(y-x) (x+y) / (y-x)(y^2+xy+x^2) = - x+y / y^2+xy+x^2