已知3x-2y-5x=0,x+2y-7x=0,xyz不等于0,求x^2-2y^2+z^2/yz的值

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知7x+5y/2y-x=3/2,且x≠0,求X/x-4y 已知:3x-5y=0,求x/y,x-y/y,x-y/x 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知(x-y)^2+|5x-7y-2|=0,求x,y的值. 已知2x-y=-3,求代数式5(x-3y)-2(x-7y) 已知|5x-y-8|+(7y-x+2)=0则4x+6y 已知x,y>0 2x+y+3=xy 求5x+4y最小值 已知2x-y/7x+5y=2/3且y≠0,求x/y的值 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x-3y=0,求(2x+y)/(x^2-2xy+y^2)X(x-y) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 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+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值 已知x>0,Y>0,如何证x^2/y+y^2/x>=x+y 已知|x+y-3|+(x-y)2=0则 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y