**
Absolute Value
** -
The absolute value of a number a, denoted |a|, is the positive
distance between the number and zero on the number
line. It is the value of the
corresponding "unsigned" number -- that is, the number with the sign
removed.

**
Boundary Point
** -
A value of the variable that makes the equation true when an equal sign is substituted for
an inequality sign (<, ≤, >, or ≥). Also called a critical point.

**
Critical Point
** -
A value of the variable that makes the equation true when an equal sign is substituted for
an inequality sign (<, ≤, >, or ≥). Also called a boundary point.