求几个方程组的答案 ｛2x+y=2 {3x-y=7 x=?y=?{x+2y=50 {3x=2y+6 x=?y=?{x+y

已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 求x+y/3+x-y/2=6 3(x+y)-2(x-y)=28方程组的解 已知x,y的值满足方程组x+2y=3,x-y=-2,求x/(x-y)²+x²-y²/(x+ 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 已知方程组{2x+y=6,x-3y=1,不解方程组,求7y(x-3y)²-(3y-x)²的值. 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 解二元一次方程组:{5(x+y)+3(x-y)=2{7(x+y)-3(x-y)=-6 2(x+y)-3(x-y)=1 6(x+y)+7(x-y)=51 解方程组 解方程组﹛2(x+y)-3(x-y)=1 6(x+y)+7(x-y)=51 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y