x^2y-3xy^2+2yx^2-y^2x
=3x²y-4xy²
3(4a^2b-5ab^2)-(3a^2b-4ab^2)
=12a²b-15ab²-3a²b+4ab²
=9a²b-11ab²
x-[3x-2(1+2x)]
=x-3x+2(1+2x)
=-2x+2+4x
=2x+2
2(x^2-xy)-3(2x^2-3xy)-2[x^2-(2x^2-xy+y^2)]
=2x²-2xy-6x²+9xy-2x²+4x²-2xy+2y²
=-2x²+5xy+2y²