Пожалуйста помогите с заданием 90

((x-y)+4xy)/((x+y)-4xy)=(x-2xy+y+4xy)/(x+2xy+y-4xy)=

=(x+2xy+y)/(x-2xy+y)=(x+y)/(x-y)=(666+333)/(666-333)-

=999/333=(3*333)/333=3*333/333=3=9.

=(x^2-2xy+y^2-4xy) /(x^2+2xy+y^2-4xy)=(x+y)^2 /(x-y)^2=(666+333)^2 /(666-333)^2=999^2/333^2=(999/333)^2=3^2=9, отв.  9