由x^2-4x+4+y^2-2/3y+1/9=0,得,
（x^2-4x+4）+（y^2-2/3y+1/9）=0,
（x-2）^2+(y-1/3)^2=0,
∴x=2,y=1/3
∴x+1/y
=2+3
=5
x^2+1/y^2
=4+9
=13