5x2*3xy=

5x2*3xy= 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2. 4x2-3xy-( )=5x2+4xy-3y2 解方程组 x2 -2xy -y2 =1 2x2 -5xy -3y2 =0 如果x2+y2=5,那么代数式(3x2-2xy-y2)-(x2-2xy-3y2)的值为 4x2-3y2+2xy-4x2+5x2 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. 已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2= 若X2+xy-2y2=0,则（x2+3xy+y2)/x2+y2=? 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 . 解方程组 x2 -2xy -y2 =1 2x2 -5xy -3y2 =0解方程组 x2 -2xy -y2 =12x2 -5xy -3y2 =0 x+y=3,xy=-5,x2+y2=19,x2-xy+y2=24,求x-y 解一元二次方程组 x2-2xy+y2=1 2x2-5xy-3y2=0补充结果 已知x/y=3/5,求 (x2-xy+2y2)/(x2+2xy-y2)的值