2x²-5x＋x²＋4x－3x² －3x²y＋2xy²＋3xy

2x²-5x＋x²＋4x－3x² －3x²y＋2xy²＋3xy (3x+2y)(9x²－6xy＋4y²﹚ 若x²＋y²=7,xy=-2,求5x²-3xy-4y²-11xy-7x² -3(xy-2x²)-[y²-(5xy-4x²)+2xy] 2x²y＋｛2xy-[x²y-2(﹣3x²y+xy)]﹣4xy²｝ 计算 3x²y+xy²-[2xy²-4x²y+（x²y-2xy²） (2x²y-3xy²)-3(x²y-2xy²)+2（x²y-4xy&# 1.若x/y=2,求分式x²－xy＋3y²／x²＋xy＋6y²的值 先化简,再求值 4（xy²＋3xy-2x²y)-[12xy-3(3x²y-2xy² 已知x／y=3,求x²＋2xy-3y²／x²－xy＋y²的值 -3(2x²-xy)+4(x²+xy-6) 求多项式½（－3xy＋2x²)－3(x²－½xy)的值,其中x＝5,y＝－8.（