Below is the graph of a circle with center at the origin and a radius of 3. Line $\small{l_2}$ is tangent to the circle at $\small{(a,b)}$, and line $\small{l_1}$ passes through the origin and intersects $\small{l_2}$ at $\small{(a,b)}$.

Using the point $\small{(a,b)}$ and the relationship between $\small{l_1}$ and $\small{l_2}$, find an equation for the family of lines tangent to this circle. Express your final answer in terms of $\small{x \;\mbox{and} \; a}$.