您的题目应该是：x^2+y^2-4x-6y+13=0,求(x-y)^-2的值.
x^2+y^2-4x-6y+13=0
（x^2-4x+4）+（ y^2-6y+9）=0
(x-2)^2+(y-3)^2=0
x-2=0,y-3=0
x=2,y=3
(x-y)^-2=1/（x-y）^2=1/(2-3)^2=1不是