题目

3(2x^y-3xy^2)-(xy^2-3x^2y),其中x+1/2,y=-1

提问时间：2020-07-24

答案

3(2x^2y-3xy^2)-(xy^2-3x^2y)
=6x²y-9xy^2-xy²+3x²y
=9x²y-10xy²
=9*1/4*(-1)-10*(1/4)*1
=-9/4-10/4
=-19/4