2A*B²-C
=2(2a²+3ab-b²)×(-1/2ab)²-(1/8a³b³-1/4a²b^4)
=2(2a²+3ab-b²)×1/4a²b²-(1/8a³b³-1/4a²b^4)
=a^4b²+3a³b³/2-a²b^4/2-1/8a³b³+1/4a²b^4
=a^4b²+11a³b³/8-a²b^4/4
2A*B²-C
=2(2a²+3ab-b²)×(-1/2ab)²-(1/8a³b³-1/4a²b^4)
=2(2a²+3ab-b²)×1/4a²b²-(1/8a³b³-1/4a²b^4)
=a^4b²+3a³b³/2-a²b^4/2-1/8a³b³+1/4a²b^4
=a^4b²+11a³b³/8-a²b^4/4