5(2/3+y)-8(x-3)=20 20(x-3)+5(2/3+y)=27

3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 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 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(