圆x^2+y^2-4x-2y-8=0的圆心如何求

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)的值 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*y)的值 x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值 两圆x^2+y^2-6x+16y=0与x^2+y^2+4x-8y-44=0的公切线条数 与圆x^2+y^2-4x=0外切,又与y轴相切的圆的圆心轨迹方程是A.y^2=8x B.y^2=8x(x>0)和y=0 C.y^2=8x(x>0) D.y^2=8x(x>0)和y=0(x 已知x^2+4y^2-2x-2x+8y+5=0,求x^2-y^2/2x^2+xy-y^2*2y-y/xy-y/(x^2+y^2/y)^2的值 圆x^2+y^2-4x-2y-8=0的圆心如何求 圆C1：X*X+Y*Y+2Y-6Y-26=0与圆C2：X*X+Y*Y-4X+2y+4=0的公切线有多少条 求以相交圆C1；x*x+y*y+4x+y+1=0及C2：X*X+Y*Y+2X+2Y+1=0的公共弦为直径的圆的方程 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 两圆x^2+y^2-4y=0和x^2+y^2-4x+8y-7=0的圆心距为…… x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值 两个圆x^2+y^2+2y+2y-2=0 x^2+y^2-4x-2y+1=0的公切线有几条 圆x^2+y^2-x=0和x^2+y^2+4y=0的位置关系 已知x^2-8x+y^2-y+16又1/4=0,求[(x+y)(x-y)-(x+y)^2-2y(x-3y)]÷4y的值 圆O1：x+y-2x=0和圆O2：x+y-4y=0的位置关系