Explain how to use the vertex and the value of a to determine the range of an absolute value function.

An absolute value function in the form ...

f (x) = a|x - h| + k

will have its vertex at (x, y) = (h, k). The sign on scale factor "a" will tell you whether it opens upward (a > 0) or downward (a < 0).

If a is positive, the vertex is a minimum, and the range is [k, ∞).

If a is negative, the vertex is a maximum, and the range is (-∞, k].