I believe it is growth, decay would be the other way around.
It’s a function because it passes the vertical line test
<span>To find the beginning position, we need to know how many feet the climber has ascended in the 6-hour time frame. At the rate of 800 feet per hour, this would total to 4,800 feet in 6 hours (800 * 6). Subtracting this amount from the final position would give the elevation at the beginning of the ascent: (11600 - 4800) = 6,800 feet above sea level to begin.</span>
