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

Вопрос от посетителя:

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

Илюха отвечает:

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