已知4x-3y=7,3x+2y=19,则14x-2y=?先谢谢大家了

已知二元一次方程x+y=7,3x+4y=19,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 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 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(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x+2y=3则x=? x-y=7则y=? 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知3x-4y=0,则x^2-y^2/x^2+y^2 已知-x+y=3,则2(x-y)2次方-4(x-y)+6 已知X和Y满足3X+4Y=2,X-Y-1/7 已知｛3x+2y=3 2x+3y=7 ,则x+y= ,x-y= 已知2x=3y,则y分之x=< >,y分之x+y=< >. 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知7x+5y/2y-x=3/2,且x≠0,求X/x-4y 已知|x+y-3|+(x-y)2=0则