[tex]\bf y=5\cdot 0.5^x\implies y=5({0.5})^x\implies y=5(1-0.5)^x\\\\
-------------------------------\\\\
\qquad \textit{Amount for Exponential Decay}\\\\
A=I(1 - r)^t\qquad
\begin{cases}
A=\textit{accumulated amount}\\
I=\textit{initial amount}\to &5\\
r=rate\to 50\%\to \frac{50}{100}\to &0.5\\
t=\textit{elapsed time}\to &x\\
\end{cases}
\\\\\\
A=5(1-0.5)^x[/tex]
so, is decaying at a rate of 0.5 or 50%, notice, since is a decay rate, is negative.
