x^2+y^2-4x+6y+13=0,则xy=?

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^2+Y^2+4X+6Y+13=0(X\Y为实数),则XY=_ 已知x^2+y^2-4x+6y+13=0求(xy+y^2/5x^2-5xy+xy+y^2)·（5/x+y）-（y/x-y 7.X*X+2X+Y*Y-6Y+10=0,则xy=? 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-y=4xy，则2x+3xy-2yx-2xy-y 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* 已知实数xy满足x^2+y^2-6x+4y+13=0求x^y的值 2 21.（2x+3y) -（x+2y) 2 2 2 22.3|x-3|+x -6xy+9y =0 则x y+2xy=? x^+2xy+y^+4=16 x^-2xy+y^=16 求(3xy+6y^)+|x^-(2xy+2y^-3x^)|的值 {x,xy,lg(xy)}={0,|x|,y} 则log8（X^2+Y^2） 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