Для упрощения данного выражения сначала найдем общий знаменатель:

(4b/(4-b) + 16/(16-b^2))(4+b)/4 - 4/(4-b) =

= (4b(16-b^2) + 16(4-b))/(4(16-b^2)) * (4+b)/4 - 4/(4-b) =

= (64b - 4b^3 + 64 - 16b)/(64 - 4b^2) * (4+b)/4 - 4/(4-b) =

= (48b - 4b^3 + 64)/(64 - 4b^2) * (4+b)/4 - 4/(4-b) =

= (4(12b - b^3 + 16))/(4(16-b^2)) * (4+b)/4 - 4/(4-b) =

= (12b - b^3 + 16)/(16-b^2) * (4+b)/4 - 4/(4-b) =

= (12b - b^3 + 16)(4+b)/(4(16 - b^2)) - 4/(4-b) =

= (4b + 48 - 4b^2 - b^4 + 16b - b^3)/(64 - 4b^2) - 4/(4-b) =

= (-b^4 - b^3 + 12b + 16)/(64 - 4b^2) - 4/(4-b)