If it looks like this
y = 161*(0.725)^t then it's a decay. Reason: the base is under 1. Try a couple of values for t say 0,1,2
y = 161 * (0.725)^0
y = 161
y = 161 * (0.725)^1
y = 161 * 0.725
y = 116.7
y = 161 * (0.725)^2
y = 161 * (0.5256
y = 84.63
You can see that the function is steadily getting smaller. Remember if the base is under 1 and more than 0 the function decays. If it is greater than 1 then the function grows.
Just to make sure we understand what I'm saying
0 < base < 1
y = a ( base)^power.
