已知2x-y=4,则7-6x+3y=?

已知(x-y)/13=y/7,则（x+y）/y=已知x/6=y/4=z/3(x,y,z均不为零）,则(x+3y)/(3y-2z)= 已知|5x-y-8|+(7y-x+2)=0则4x+6y 已知-x+y=3,则2(x-y)2次方-4(x-y)+6 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x,y为实数,根号3x+4 +y^2-6Y+9=0则x+y=? 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 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 已知4x-3y-6z=0,x+2y-7z=0,则x-y+z/x+y+z=_________ 已知4x-3y+6z=0 x+2y-7z=0 则x-y+z/x+y-z=? 已知{4x-3y-6z=0、x+2y-7z=0,则x-y+z：x+y+z= 已知x+2y=3则x=? x-y=7则y=? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 已知(3x+y+6)²+|x+y+2|=2,则x=,y=. 已知x-2y=3,则(2x+y-6)/(3x-y-9)=? 已知3x-4y=0,则x^2-y^2/x^2+y^2 已知2x-y=4,则7-6x+3y=? 已知X和Y满足3X+4Y=2,X-Y-1/7