For
![f(x)=3\left((5)/(4)\right)^(x)](https://img.qammunity.org/2019/formulas/mathematics/college/uhqb1rb387dpwja85onf8bwk1aa2puce0r.png)
you seem to want to know the value of f(0). Put 0 where x is, then evaluate.
The initial value of the function is 3._____
You will observe that when x=0, the exponential term evaluates to 1. This is true regardless of its base. Thus f(0) is always the coefficient of the exponential term—in this case, 3.