｛5x+2y=18,y=－x

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 ｛5x+2y=18,y=－x 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 2(x-y)=5y,x-y=-5 x-y / 5y= (y-x)^2 / ( ) x*x+2x+y*y-4y+5=0 x= y= x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 求(X+Y)(X-Y)(X²+Y²),X=5 Y=2, (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 解方程组：2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66 解方程组:2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66