A.x+5y=2,xy=7 B.2x+1/y=1,3x-4y=0 C.3x=5y,x/4+y/3=4/3 以上三组哪组属

A.x+5y=2,xy=7 B.2x+1/y=1,3x-4y=0 C.3x=5y,x/4+y/3=4/3 以上三组哪组属 若x+y=-1,则x^4+5x^3y+x^2y+8x^2y^2+xy^2+5xy^3+y^4=( ) 已知A=x^3+3x^2y-5xy^2+6y^3-1,B=y^3+2xy^2+x^2y-2x^3+2,C=x^3-4x^ 已知x,y>0 2x+y+3=xy 求5x+4y最小值 已知A=5x^+2xy-4y^,B=-x^-4xy+y^,C=x^-xy+3y^其中xy满足|2x+1|+(y-4)^= 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} [-(x-y)^2/xy]^-4*(y^2-xy/x)^3*(x^4/y^10)÷(xy-y^2/x)^-5=-y(y- (3x-2y)(4x-5y)-11(x+y)(x-y)+5xy,已知X=3又1/2,y=2又1/3 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 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（x+2）^2+|x+y+5|=0,求3x^2y-[2x^2y-(2xy-x^2y)-4x^2]-xy 已知(x+2)^2+|x+y+5|=0,求3x^2y+{-2X^2y-[-2xy+(x^2y-4x^2)]-xy}