1、x+2y=5 2、-2x-y=-8 3、4x+y12 4、5x-3y=18 用二元一次方程我妈马上就要来检查了

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? {x+y=1 ,xy=-6{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) {x+y=5 2x-1y=8 y=8-2x 5x-y=-1 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 x+y=8 2x-y=1 求3x+5y 分式的加减:[(x/y-y/x)除以（x+y）+x（1/y-1/x)]除以1+x/y,其中x=5,y=2 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 解下列方程组：{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 先化简,再求值[(2x+y)^2-(2x+y)(2x-y)-y(5x+y)]÷(1/2y),其中x-y=2