(1)3m²n+5mn²+6nm²-4n²m-n²m
=(3m²n+6nm²)+(5mn²-4n²m-n²m)
=9m²n
(2)2/3a²-6a³+5a-1/4+5a³-1/2-4/3a²
=(2/3a²-4/3a²)-(6a³-5a³)+5a-(1/4+1/2)
=-2/3a²-a³+5a-3/4
(1)3m²n+5mn²+6nm²-4n²m-n²m
=(3m²n+6nm²)+(5mn²-4n²m-n²m)
=9m²n
(2)2/3a²-6a³+5a-1/4+5a³-1/2-4/3a²
=(2/3a²-4/3a²)-(6a³-5a³)+5a-(1/4+1/2)
=-2/3a²-a³+5a-3/4