{x+y=5 2x-1y=8

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=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 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 {x+y=5 2x-1y=8 y=8-2x 5x-y=-1 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? x+y=8 2x-y=1 求3x+5y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 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 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 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 方程组：x(y+1)+2(y+1)=y(y-1)x-5(y-1) x（4+y）-y（8-x）=-20x(y+1)+2(y+1)=y(y-1)x-5(y-1) x（4+y）-y（8-x）=-20（这是一个方程组.） (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 化简求值:8(x+y)+2(x-y)平方-5(x+y)-(x-y)平方-2,其中,x=2,y=1 已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值 先化简,再求值[(2x+y)^2-(2x+y)(2x-y)-y(5x+y)]÷(1/2y),其中x-y=2