Answer:
distance between a number and zero
|a| = a if a >= 0 and |a| = -a if a < 0
|4| = 4 and |-4| = 4
nonnegative
symmetric over the y-axis
left line is y = -x for x < 0
right line is y = x for x >= 0
Axis of symmetry: y-axis
Vertex: (0, 0)
