3x²y－﹛xy－[3xy－（4xy²+½xy）]－4x²y﹜

3x²y－﹛xy－[3xy－（4xy²+½xy）]－4x²y﹜ 3x²y+xy²-[2xy²-4x²y+（x²y-2xy²） 计算 2xy[4x²y²-3y（xy+x²y）-xy²] -3(xy-2x²)-[y²-(5xy-4x²)+2xy] (2x²y-3xy²)-3(x²y-2xy²)+2（x²y-4xy&# 已知x²-xy=4,y²-xy=9求下面代数式的值（1）x²－2xy＋y²；（2 3(x²-2xy)-2(－3xy+y²) 计算：(xy-x²)×x-y/xy 化简4xy-3y²-3x²+xy-3xy-2x²+x²-2y² (3x+2y)(9x²－6xy＋4y²﹚ 1.先化简再求值（½ x²y＋1／5 xy²－¼xy)·(-½xy&# -4x²y-8xy²+2x²y-3xy²