原式=2x^2y-2xy^2-(-3x^2y^2+3x^2y^2-3xy^2)
=2x^2y-2xy^2-(-3xy^2)
=2x^2y-2xy^2+3xy^2
=2x^2y+xy^2
=2×1×2+（-1）×4
=4-4
=0