Изменения

\dfrac{A}{(1+z)}+\dfrac{Bz+C}{(1-z)^2} =\dfrac{1}{1+z} + \dfrac{-z+7}{(1-z)^2}=\dfrac{1}{1+z}+\dfrac{7}{(1-z)^2}-\dfrac{z}{(1-z)^2}.