圆x^2+y^2-6x-2y-15=0的半径为?

x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x,y 满足x(x-2)-y(y-6)=-10,求x,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 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 x^2+4y^2-6x+4y+10=0,求x^4-y^4/(x+2y)(x-2y)*x+2y/xy^2+y^3除以（x^2+y^2/y)^2的值 求f(x,y)=x+y+7的最大值,使(x,y)满足x+2y≤10,2x+y≥6,y≥0 解方程组 10（x-y)=3(x+y)+15 6(x+y)=4(2x-y)+1610（x-y)=3(x+y)+156(x+y)=4(2x-y)+16分开的。 化简求值：已知x、y满足：x^2+y^2-4x+6y+13=0 求代数式 的值.(3x+y)^2-3(3x-y)(x+y)-(x-3y)(x+3y)急用！ x^2+y^2+6x-4y+13=0求x,y,x^2-y^2的值 已知x^2+y^2+6x-2y+10=0,求x+y/x-y的值谢谢 已知x^2-2x+y^2+6y+10=0,求分式x-y/x+y的值 已知x^2+y^2-6x-8y+25=0,求分式y/x - x/y的值 已知x^2+y^2-6x-8y+25=0 求y/x-x/y的值 已知x,y满足x^2+y^2-6x+8y+25=0,求y^x的值 若x^2+y^2-6x+8y+25=0 则y/x-x/y的值是 已知：4x^2+y^2-4x-6y+10=0,求y/x-x/y的值