已知y-x=2,x-3y=1,则x^2-4xy+3y^2的值为

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知2x=3y,则y分之x=< >,y分之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x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 比例线段：已知x/y=2/3,则 x/x+y= ,x-y/x+y= 要过程! 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知|x+y-3|+(x-y)2=0则 已知f(x+y,y/x)=x^2-y^2,则f(x,y)= 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 1 已知1/X+1/Y=1/X+Y 则 Y/X+X/Y=2 已知1/X-1/Y=5,则3X+5XY-3Y/X-3XY-Y= 已知x=2+根号3,y=2-根号3,计算代数式(x+y/x-y-x-y/x+y)乘以(1/x^2-1/y^2) 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 已知1/x-1/y=3,则代数式x(2-7y)-y(7x+2)/x(1-y)-y(x+1)的值为多少. 已知x+y+2(-x-y+1)=3(1-y-x)-4(y+x-1),则x+y等于多少 已知(1/X )-(1/Y)=1,则(2X+3X-2Y)/(X-2XY-Y)=?