x^3y^3-(1/2)x^y+y^-2x^3y^3+0.5x^+y^+x^3y^3-2y^-3
=(1-2+1)x^3y^3-(1/2)x^y+0.5x^+(1+1-2)y^-3
=-(1/2)x^y+0.5x^-3,
请检查题目哪一步没看明白？