If we consider a, b and c all positive constants and b > 1, a exponential growth in general is represented by a function like:
[tex]f(t)=a\cdot b^{ct}[/tex]
In otherwise, a exponential decay can be represent by:
[tex]g(t)=a\cdot b^{-ct}=a\cdot(\frac{1}{b})^{ct}[/tex]
Now we can check whose functions are similar to one of these:
h(x) = 3x + 1.3 is a linear function, therefore, this is neither exponential growth or decay;
f = 3*(4.2^x) is an exponential growth;
y = (5/6)*(7^x) is an exponential growth;
T = 0.6*(1.3^x) is an exponential growth;
W(x) = (1/8)*[(3/5)^x] is an exponential decay, since in this case we have 3/5 < 1.
K = 4.2*(0.28^x) is an exponential deacay by the same argument.
