7. find the circumcenter of triangle abc.
(0, -1)
(0, -3)
(-4, -1)
(-4, -3)

The circumcenter of a triangle is the point where the perpendicular bisectors of the sides intersect.
from the graph, we can see that the perpendicular bisector of BC is the y axis, x=0, the perpendicular bisector of AC is y=-3, so the circumcenter is (0,-3)