2/3a-{1/3a^2+【(3a^2-5a+1)-1/3a-5]}
=2/3a-{1/3a²+3a²-5a+1-1/3a-5}
=2/3a-(10/3a²-16/3a-4)
=2/3a-10/3a²+16/3a-4
-10/3a²+14/3a-4