已知A=x^3-2y^3+3x^2y+xy^2-3xy+4,B=y^3-x^3-4x^2y-3xy-3xy^2+3,C=y^3+x^2y+2xy^2试说明对于xyz的任何值,A+B+C都是常数

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知方程组 2x+y=3a x-2y=a 求x/y 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知3x+2y=a,2x+3y=b,则(x+y)(x-y)=? 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 1、(-y^3)^5/y^3/ y^2+2(-y)^102、(x-y)^7/(y-x)^6+(x+y)^3/(x+y)^23、已知X^a=5,x^b=3,求X^(3a-2b)的值 已知关于x、y 的方程组x-y=a+3与2X+Y=5的解x、y满足x>0,y 已知2x=3y,则y分之x=< >,y分之x+y=< >. 已知x=3分之一,y=-2分之一,求代数式x-(x+y)+(x+2Y)-(x+3y)+(x+4y)...-(x+2009y) 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知x-3y=0,求(2x+y)/(x^2-2xy+y^2)X(x-y) 比例线段：已知x/y=2/3,则 x/x+y= ,x-y/x+y= 要过程! 已知|x+y-3|+(x-y)2=0则 初一因式分解练习题,谁好心帮我解下表示平方1.2X~-3XY-X2.(X+Y)~(X+Y)(X-Y)(X+Y)(Y+Z)3.3X(a+2b)~-6XY(a+2b)4.a(x-y)-b(X-Y)-C(Y-X)5.(b-a)~-2a+2b6.(x-y)~-m(y-x)+y-x7.x(x-y)(a-b)-y(y-x)(b-a)8.已知a+b=13,ab=40,求 b+ab~的值