х(1-у)+z(1-y)/(1-у3)-3у(1-у) = x+z/(1-y)^2
(x+z)(1-y)/(1 – у)*(1 + у + у^2)-3у(1-у) = x+z/(1-y)^2
(x+z)(1-y)/(1 – у)*(1 +у + у^2-3у) = x+z/(1-y)^2
(x+z)(1-y)/(1 – у)*(у^2-2у+1) = x+z/(1-y)^2
x+z/*(у^2-2у+1) = x+z/(1-y)^2
(x+z)/*(у^2-2у+1) = x+z/(1-y)^2
(x+z)/*(1-у)^2= x+z/(1-y)^2
