x^2+(y-2)^2=0是X(y-2)=0的什么条件（充分条件,必要条件,充要条件）

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 请问这道数学题是否是这样做?x^2-y^2=(x-y)(x+y)(x-y)=(x-y)x+y=0 X+Y/X=2,X/Y=?是（x+y）/x=2哦 若x-y不等于0,2x-3y=0,则分式(10x-11y)/(x-y)的值是（）?(10x-11y)/(x-y) =[(8x-8y)+(2x-3y)]/(x-y) =8为什么8X-8Y=8？(10x-11y)/(x-y)=[(8x-8y)+(2x-3y)]/(x-y)=8+(2x-3y)]/(x-y)=8+0=8 若x^2+y^2-6x+8y+25=0 则y/x-x/y的值是 x,y>0,且x+2y=1,u=(x+1/x)(y+1/(4y)最小值是: 已知x>0,Y>0,如何证x^2/y+y^2/x>=x+y (X,Y) f(x,y)={12y^2,0 x*x+2x+y*y-4y+5=0 x= y= 设Z=X+Y,其中X,Y满足X+2Y>=0,X-Y 化简y(x+y)+(x+y)(x-y)-x^2 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 紧急!(X-Y)^3*(X-Y)^2*(Y-X)(X-Y)^3*(X-Y)^2*(Y-X)得数是（X-Y)*(Y-X)吗?如果不是.. 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知X*X+Y*Y+6X-8Y+25=0 求（Y/X)+(X/Y)-2=? 设x大于1,y大于0,x^y+x^-y=2根号二,x^y-x^-y等于?