x^2+4y^2-4x+20y+8=0,求x+y=____.

已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 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 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y* 已知x^2+4y^2-4x+8y+8=0,求x+y 已知方程组4x+2y=1,20x+8y,求x,y 已知4x=9y求(1)x+y/y (2)y-x/2x 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)& 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 已知x^2+4y^2-4x+4y+5=0,求(y^4-x^4)/(y-2x)(x+y)*2x-y 已知2x-y=10,求[(x²+y²)-(x-y)²+2y(x-y)]/4y 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值