4x2-3xy-( )=5x2+4xy-3y2

4x2-3y2+2xy-4x2+5x2 4x2-3xy-( )=5x2+4xy-3y2 (x2+xy+y2)-4xy(x2+y2) 5x2*3xy= 若3x2-4xy+y2=-3,2x2+3xy-2y2=8,求5x2-18xy+7y2的值. 已知x2+y2 =7,xy=-2.求5x2 -3xy-4y2 -11xy-7x2 +2y2 已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值 5x2-3xy-4y2-11xy+(-7x2)-(-2y2),其中x2+y2=7,xy=-2,求值 已知X2+y2=7,Xy=-2,求多项式5X2一3Xy-4y2-11Xy-7X2+2y2的值. 解二元二次方程组｛x2-4xy+3y2=0 3x2+xy=20 先化简,再求值：5x2-[2xy-3（xy+2）+4x2] ,其中x=-2,y= .先化简,再求值：5x2-[2xy-3（xy+2）+4x2] ,其中x=-2,y=1/2 . 已知:x2+y2=7,xy=-2.求7x2-3xy-2y2-11xy-5x2+4y2已知:x2+y2=7,xy=-2.求7x2-3xy-2y2-11xy-5x2+4y2 已知X2次方+XY=3,XY+Y2次方=-2,求下例值:X2次方+4XY+3Y2次方 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2. x2+y2+2xy=256 x2+y2-2xy=4 (x2, (3/2x2-5xy+y3)-【-3xy+2(1/4x2-xy)+2/3y2】,其中/x-1/+(y+2)2=0 (x2+xy+y2)-4xy(x2+y2)因式分解 解方程组x2+xy=12 xy+y2=4