①-1/3（9x^2-3)+6(2/3x^2+1)②x^2y-(6xy+3x^2y-xy^2)+（5xy+2x^2y)过程
问题描述：
①-1/3（9x^2-3)+6(2/3x^2+1)②x^2y-(6xy+3x^2y-xy^2)+（5xy+2x^2y)过程
答
①-1/3（9x²-3)+6(2/3x²+1)
=-3x²+1+4x²+6
=x²+7
②x²y-(6xy+3x²y-xy²)+（5xy+2x²y)
=x²y-6xy-3x²y+xy²+5xy+2x²y
=xy²-x²y