(36-у^2)/(y-8) *[y/(y-6) - 2y/(y^2-12y+36)] + 12y/(y-6)=
(6^2-y^2)(y-8) * [y/(y-6) - 2y/ (y-6)^2] +12y/(y-6)=
(6-y)(6+y)/(y-8) *[y(y-6)-2y/(y-6)^2] + 12y/(y-6)=
-(y-6)(y+6)/(y-8)*(y^2-6y-2y)/(y-6)(y-6) +12y/(y-6)=
в первом множителе (y-6) сократить, получим:
-(y+6)* (y^2-8y)/(y-8)*(y-6) + 12y/(y-6)=
[-(y+6)(y^2-8y) + 12y(y-8)]/(y-8)(y+6) =
[-(y+6)*y*(y-8) +12y(y-8)]/(y-8)(y-8) =
(y-8)[-y(y+6)+12y]/(y-8)(y-6) =
(y-8) сокращаем, получим:
(-y^2+6y)/(y-6) =
-y(y+6)/y-6