若x-2y=3,则2x-4y-7=这是几年级的

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 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 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 若2x=3y,则(x*x+y*y)/x*x=? 若5x+3y=3x+4y=x+2y+6,则x+y=___ 若x+3y=3x+2y=7,则x+y=几? 若x/y=4/3 则3x+2y/2x-5y= 若x-2y=3,则2x-4y-7=这是几年级的 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 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,z成等差数列,则(z-x)^2-4(x-y)(y-x)= 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 已知（x+y）2 =2,(x-y)3 =3,求(x+y)7(x-y)2(x+y)3(y-x)4 的值 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 2x-y/x+y=4,则4x-2y/2x+2y+3x+3y/2x-y 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=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值?