The range describes all the y-values used by the graph. It's basically describing how low to how high the graph goes.
This graph tops out at a y-value of 12. (see the graph below)
There is no bottom to the graph, since it goes down forever.
Even though we thought of it from top to bottom, we have to describe it from bottom to top:
- infinity < y ≤ 12
We use "<" on infinity, because we never get there.
We use "≤" on 12, because 12 is actually used as the y-value at the top.