已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2.

已知x2-xy=3，xy-y2=-5，试求代数式x2+2xy-3y2的值． 已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值 已知X2+y2=7,Xy=-2,求多项式5X2一3Xy-4y2-11Xy-7X2+2y2的值. 已知：x2+y2=7，xy=-2．求7x2-3xy-2y2-11xy-5x2+4y2的值． 已知x2+y2 =7,xy=-2.求5x2 -3xy-4y2 -11xy-7x2 +2y2 已知2x=3y,求xy／(x2+y2)-y2／(x2-y2)的值 已知x2-xy=-3，2xy-y2=-8，求2x2+4xy-3y2的值． 已知x2+xy=-3，xy+y2=7，试求：x2+2xy+y2的值． 已知:x2+y2=7,xy=-2.求7x2-3xy-2y2-11xy-5x2+4y2已知:x2+y2=7,xy=-2.求 已知，A=3x2+3y2-5xy，B=2xy-3y2+4x2，求： 已知X2次方+XY=3,XY+Y2次方=-2,求下例值:X2次方-Y2次方 已知x2;+xy=3,xy+y=-2,求代数式2x2;-xy-3y2;的值