若X+Y=6,X^2-Y^2=42,则X-Y=?

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若X+Y=6,X^2-Y^2=42,则X-Y=? 若f(x+y,y/x)=x^2-y^2,则F(X,Y)= 若2x=3y,则(x*x+y*y)/x*x=? 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 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=6,x^2-y^2=24,则x+y=? 若x^2-y^2=6 x+y=3 则x-y=多少 若2x+2y=6x-3y,则x比y= 若x^2+y^2-10x+6y+34=0,则x+y=? 若x^2+y^2+2x+10=6y,则y^x等于? 若x^2+2x+y^2-6y+10=0,则x-y 若x,y,z成等差数列,则(z-x)^2-4(x-y)(y-x)= 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x=