x^2+y^2+16x-4y+68=0,则x+y=?

x^2+y^2+16x-4y+68=0,则x+y=? 已知X^2+Y^2+16X-4Y+68=0,则X+Y=----------- x*x+2x+y*y-4y+5=0 x= y= x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)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 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? x*x+4y*y+2x*x-4y+2=0求根号下5x*x+16y*y的值快啊 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x-4y)(2x+y)= 若x*x+4*y*y+2*x-4*y+2=0,求5*x*x+16*y*y的算术平方跟 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 x*x+y*y-2x+4y+5=0求x, 若x-y=1 化简（x+y)(x^2+y^2)(x^4+y^4)(x^8+y^8)(x^16+y^16) 已知x^2+y^2+13-4x+6y=0,求(2x-y)^2-2(2x-y)(x+2y)+(x+2y)^2 .先化简再求值：（2x+y）（2x+y)-(2x-y)平方其中X,Y满足X平方+Y平方-2X+4Y+5=0 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 {4x-3y-10=0 3x-2y=0,{3x-4(x-y)=2 2x-3y=1,{2(x+y)-(x-y)=3 (x+y)-2(x-y)=1