4. The equation of the tangent line passing through the point $\mathrm{P}\left(-\frac{1}{3}, \frac{2 \sqrt{2}}{3}\right)$ on the circle $\mathrm{x}^{2}+\mathrm{y}^{2}=1$ is $\qquad$ ,
$4 . x-2 \sqrt{2} y+3=0$