若x-y=9,则X^2+y^2=91,x*y=?

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若x-y=9,则X^2+y^2=91,x*y=? 若f(x+y,y/x)=x^2-y^2,则F(X,Y)= 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 若2x=3y,则(x*x+y*y)/x*x=? 若2x+3y=2004,则代数式2(3x-2y)-(x-y)+(-x+9y)=... 若2x+y=2012,则代数式2(3x-2y)-(x-y)+(-x+9y)= 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 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x= 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 若x+2y分之x-y=3,则代数式x+2y分之2（x-y)-3(x-y)分之x+2y的值为 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（） 设f(x+y,x-y)=x^2-y^2,则f(x,y)= 已知f(x+y,y/x)=x^2-y^2,则f(x,y)= 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 x（x-2y）=y(2y-x) ,则y分之x是多少