化简:(2xy-y2)-(—y2+xy)=

化简:(2xy-y2)-(—y2+xy)= (x2+2xy+y2)( x2-xy+y2)2 化简 -（x2-2xy-y2)+(5x2-2xy-3y2)-（x2-2xy-y2)+(5x2-2xy-3y2)化简 化简(X2+y2-z2-2xy)/(x2-y2+z2-2xy)/(x2-y2-z2+2xy)(x2+y2-z2+2xy) (x2-2xy+y2)-(x2+2xy+y2)=什么 ( x2+xy+y2) ( x2+xy+2y2)-12y4 x2-2xy+y2-9 (2x2-3xy+4y2)+(x2+2xy-3y2）化简（要有过程） x2—2xy=3y2 2xy+y2=1 怎么解这个方程组? (x2+xy+y2)-4xy(x2+y2) 计算：(xy-x2)÷xy分之x2-2xy+y2 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=? 2(x2-xy)-3(2x2-3xy)-2[x2-(2x2-xy+y2)] 化简. 已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值 (x2+y2)(x2-xy+y2)-2x2y2因式分解 已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2= 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2.