\[A(t)=A_0(1+r)^t,\qquad A(t)=A_0e^{kt},\]
\[A(t)=P\left(1+\frac rn\right)^{nt},\qquad P(t)=\frac{d}{1+ke^{-ct}}.\]
\[\log_b(MN)=\log_bM+\log_bN,\] \[\log_b(M/N)=\log_bM-\log_bN,\] \[\log_b(M^p)=p\log_bM,\qquad \log_bx=\frac{\ln x}{\ln b}.\]