Упростите выражение 12/d-7 - 7d/(d-7)^2 - 5d/d^2-49

12 / (d - 7) - 7d / (d - 7)^2 - 5d / (d^2 - 49) =

= (12(d^2 - 49) - 7d(d + 7) - 5d(d - 7)) / ((d^2 - 49)(d - 7)) =

= (12d^2 - 588 - 7d^2 - 49d - 5d^2 + 35d) / ((d - 7)^2(d + 7)) =

= (-14d - 588) / ((d - 7)^2(d + 7)) = - (14(d + 42) / ((d - 7)^2(d + 7)).

Ответ: - (14(d + 42) / ((d - 7)^2(d + 7)).