5. Determine the type of quadrilateral whose vertices are the points of intersection of the lines:

\[
y=x+3, y=x-3, y=-x+3, y=-x-3 .
\]
5. A square with vertices at points \(A(0 ; 3), B(0 ;-3) ; C(3 ; 0)\), \(D(-3 ; 0)\).