2x2＋2y2－2（2x2＋xy－3y2＋xy）4x2－2y2＋xy2－3（－3x2＋5y2－2xy2）-4ab+5ac-3bc+5ab-6ac-6cbyx²－y＋x²y＋x－2（xy²-yx） 5x²−6x³+3x³−2x+3x²+x²−x³−x

求证:(x2-xy+y2)3+(x2+xy+y2)3能被2x2+2y2整除 若X2+xy-2y2=0,则（x2+3xy+y2)/x2+y2=? 解方程组：{3X2－2XY－Y2=O.X2+Y2＝40} 是｛3X2－2XY－Y2＝O。X2＋Y2＝40。｝ (x2+2xy+y2)( x2-xy+y2)2 化简 (x2-2xy+y2)-(x2+2xy+y2)=什么 ( x2+xy+y2) ( x2+xy+2y2)-12y4 x2-2xy+y2-9 4x2-3y2+2xy-4x2+5x2 (x2+y2)(x2-xy+y2)-2x2y2因式分解 2x2-xy+3y2因式分解 x2 y2+3xy+2 因式分解 x2-3y2=2xy过程 2X2-3XY-Y2分解因式! 4x2+3xy-2y2因式分解 -（x2-2xy-y2)+(5x2-2xy-3y2)-（x2-2xy-y2)+(5x2-2xy-3y2)化简 已知x/y=2/7,则x2－3xy＋2y2／2x2－3xy＋7y2的值是多少? 2(x2-xy)-3(2x2-3xy)-2[x2-(2x2-xy+y2)] 化简. x2－(a＋b)xy+aby2 x2+4xy－5y2 x2－5x+3 2x2+xy－y2－4x+5y－6