Помогите сократить дробь.
X(1-y)+z(1-y)/1-3y+3y^2(1-y)=x+z(1-y)/1-3y+3y^2=x+z(1-y)/1+3y^2-3y=x+z(1-y)/1-3y(1-y)=x+z/1-3y