1.x²y-3xy²+2yx²+y²x
=(x²y+2yx²)-(3xy²-y²x)
=3yx²-2xy²
=(3yx+2xy)(3yx-2xy)
=5xy²
5(a²b-3ab²)-2(a²b-7ab²)
=5a²b-15ab²-2a²b+14ab²
=3a²b-ab²
2.（1）（4a+3a²-3+3a³）-（-a+4a³)=(-8+12-3-24)-(2-32)
=7
(2）（2x²y-2xy²）-[（-3x²y²+3x²y）+（3x²y²-3xy²）]=