解
-3x²y+2x²y+3xy²-2xy²
=(-3x²y+2x²y)+(3xy²-2xy²)
=-x²y+xy²
4a²+3b²+2ab-4a²-4b²
=(4a²-4a²)+(3b²-4b²)+2ab
=2ab-b²
2a²b+3a²b-1/2a²b
=(2+3-1/2)a²b
=9/2a²b
a³+a²b-ab²+a²b-ab²+b³
=a³+(a²b+a²b)+(-ab²-ab²)+b³
=a²+2a²b-2ab²+b³
解
-3x²y+2x²y+3xy²-2xy²
=(-3x²y+2x²y)+(3xy²-2xy²)
=-x²y+xy²
4a²+3b²+2ab-4a²-4b²
=(4a²-4a²)+(3b²-4b²)+2ab
=2ab-b²
2a²b+3a²b-1/2a²b
=(2+3-1/2)a²b
=9/2a²b
a³+a²b-ab²+a²b-ab²+b³
=a³+(a²b+a²b)+(-ab²-ab²)+b³
=a²+2a²b-2ab²+b³