[tex]f(x)=3(3)^{-x}=3\left(\dfrac{1}{3}\right)^x=\left(\dfrac{1}{3}\right)^{x-1}[/tex]
[tex]f(x)=a^x\\if\ a\in(0;\ 1)\ then\ a\ function\ is\ decreasing\\if\ a > 1\ then\ a\ function\ is\ increasing[/tex]
[tex]f(x)=\left(\dfrac{1}{3}\right)^{x-1}\to a=\dfrac{1}{3}\in(0;\ 1)\\The\ function\ is\ decreasing[/tex]
[tex]f(0)=\left(\dfrac{1}{3}\right)^{0-1}=\left(\dfrac{1}{3}\right)^{-1}=3^1=3\to(0;\ 3)[/tex]
Answer: Graph C.
