W = 20e-kt
Find dW/dt
????
\(\begin{array}{|rcll|} \hline W &=& 20e^{-kt} \\ \frac{dW} {dt} &=& 20\cdot e^{-kt} \cdot (-k) \\ \frac{dW} {dt} &=& -20k e^{-kt} \\ \hline \end{array}\)
