原式=-3x³y³+6x^4y^4+4x²y³*2x²y
=-3x³y³+6x^4y^4+8x^4y^4
=-3x³y³+14x^4y^4
=-3(xy)³+14（xy）^4
=3+14=17
(x^4和y^4的意思是x的四次方和y的四次方)