There are a number of things you did not say that must be true in order to make any sense of this. I presume that the problem also tells you that point where line and circle intersect is one solution to the equation. Further, I assume that when you say a "line at 60 degrees" you mean at 60 degrees to the x-axis. The four roots of lie on a circle of radius 90 degrees apart around the circle. You are told that one root lies on the line at 60 degrees (to the x-axis presumably) so the others lie on that same circle with angle at 60+90= 150 degrees, 60+180= 240 degrees, and 60+ 270= 330 degrees. Since the circle has radius 2, . You should be able to use simple trigonometry to find each of the four roots in "a+ bi" form.