1≤x2+y2≤4则x2-2xy+3y2的取值范围英文字母后面的2是平方

若X2+xy-2y2=0,则（x2+3xy+y2)/x2+y2=? (x2+xy+y2)-4xy(x2+y2) 已知x2+4y2+x2y2+1=6xy,则(x4-y4)/(2x2+xy-y2)*(2x-y)/(xy-y2)/(x2+y2/y)2= 4x2-3y2+2xy-4x2+5x2 1≤x2+y2≤4则x2-2xy+3y2的取值范围英文字母后面的2是平方 4x2+3xy-2y2因式分解 已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2= 解方程组 ｛3x2-y2=8 {4x2+12xy+9y2=1 {x2+2xy+y2-4=0 x2+xy+y2=4 4x2-9y2=0 x2-2xy+y2-1=0还有{x2+y2=4xy-y2+4=0x2-----x的平方 y2------y的平方 还有{2x-3y=12x2-3xy+y2-4x+3y-3=0 计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/（x2+2xy-3y2） 求证:(x2-xy+y2)3+(x2+xy+y2)3能被2x2+2y2整除 (2x2-3xy+4y2)+(x2+2xy-3y2）化简（要有过程） x2+3xy+2y2=0,则x2+y2/xy 解方程组 x2+2xy+y2-4=0 x2-2xy+y2-1=0 解方程组 x2 -2xy -y2 =1 2x2 -5xy -3y2 =0 分解因式：1、a2b2-0.01 2、-xy-x2-y2 3、x2-xy+四分之一y2 2x2+xy-3y2+x+4y-1因式分解 4x2-y2/x2-2xy+y2 +(2x-y)/2x2-2xy x2+y2+2xy=256 x2+y2-2xy=4 (x2,