若x-y=2,则 =4；若2x-6y=8,则 =4若x-y=2,则 =4；若2x-6y=8,则 =4

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 若5x+3y=3x+4y=x+2y+6,则x+y=___ 若x^2+y^2-6x+8y+25=0 则y/x-x/y的值是 若X+Y=8,(X-Y)^2=4,则X^2+Y^2= 若f(x+y,y/x)=x^2-y^2,则F(X,Y)= 若x,y,z成等差数列,则(z-x)^2-4(x-y)(y-x)= 若x-y=1 化简（x+y)(x^2+y^2)(x^4+y^4)(x^8+y^8)(x^16+y^16) 若x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 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 若实数X,Y满足X²+Y²+4X-2Y +1=0,则X²-6X+Y²-2Y的最大值是多少 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2x=3y,则(x*x+y*y)/x*x=? 若2x^2-6xy+9y^2-4x+4=0,则y/x-x/y=若2x^2-6xy+9y^2-4x+4=0,则y/x-x/y=? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若5x-4y=6,4x-5y=8,则x+y=( ),x-y=( ) 若x=2012,y=2013,则(x+y)×[(x^2+y^2)/x^4-y^4)] 若2X+3Y-1=Y-X-8=X+6则2X+Y=