x+y=25 1700x+1800y=4400 的二元一次方程组

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 化简 x / y(x+y) - y / x(x+y) = 7x:4y,x:y=( ):( (x-4y)(2x+y)= 5x-4y(y-x)=? 已知x的平方+y的平方-8x+6y+25=0,求(x-y+4xy/x-y)(x+y-4xy/x+y) 已知x²+y²-8x+6y+25=0,求（x-y+4xy/x-y）（x+y-4xy/x+y） x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的值 x+x+x+y=60 .x-y=4 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=? 3（x+y）-4（x-y）=25 x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? y=x(x 已知x²+y²+8x+6y+25=0,求x-4y/x+y的值 x,y属于R*,且x+y=1,求证:(1)(x+1/x)(y+1/y)≥25/4