若3x=4,9y=7,3（x-2y）=

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 若3x=7y,则y分之x= ,x:（x:y）= 若3x=7y,则y比x= ,x:（x+y）= 9y=3x-(x-1),4(x+y)-(2x+4)=8y 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? 若X=负四分之一,能否确定代数式(2X-Y)(2X+Y)+(2X-Y)(Y-4X)+2Y(Y-3X)的值? ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20