X+Y=10,X^3+Y^3=400,求X^2+Y^2

已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 已知：3x=8y.求（1）x+y/y (2)2x+3y/x-2y 已知xy=-2,x-y=3,求（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y 已知x-3y=0,求(2x+y)/(x^2-2xy+y^2)X(x-y) 1奥数题x-2y/x+2y=3,求x-2y/3(x+2y)-3(x-2y)/x-2y的差 已知2x-y/x+2y=3,求2(2x-y)/x+2y-9(x+2y)/2x-y+3的值. 已知x+y分之x-y=2,求2x+2y分之x-y-3x-3y分之2x+2y的值 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} 当2x-y/x+y=3时,求代数式2x-y/2x+2y+x+y/6x-3y的值. 已知2x-y/x+3y=2,求代数式4x-2y/x+3y减4x+12y除以2x-y