Respuesta :
4(a²+3)-(a²+4)(a²+2)-9a =
= 4a²+12-(a⁴+2a²+4a²+8)-9a=
= 4a²+12-a⁴-2a²-4a²-8-9a =
= -a⁴+4a²-2a²-4a²-9a-8 =
= a⁴-2a²-9a-8.
= 4a²+12-(a⁴+2a²+4a²+8)-9a=
= 4a²+12-a⁴-2a²-4a²-8-9a =
= -a⁴+4a²-2a²-4a²-9a-8 =
= a⁴-2a²-9a-8.