I'm not sure about the answer myself, but here is how I think you would solve it.
First, you'd graph the circle. I recommend using a graphing calculator to do so.
Since the line is tangent and is meeting at the point (1,2) we can keep this in mind when creating our equation. From there, using what you know try to find a second point on the line.
From here it becomes normal algebra, use slope intercept form to create an equation.
I hope this helps!
