7. A line passing through the origin is tangent to the circle $x^{2}+y^{2}+4 x+3=0$. If the point of tangency is in the third quadrant, then the equation of the line is $\qquad$ .
7. $y=\frac{\sqrt{3}}{3} x$ Hint: $(x+2)^{2}+y^{2}=1$, center $(-2,0)$, radius is 1, by plane geometry, the angle of inclination of the required tangent is $30^{\circ}$.