Exponential growth
For exponential growth, the value $N(t)$ for the same time period ($c$) is always multiplied by the same factor ($d$).
The general equation of exponential growth is:
$N(t)=N_{0}\cdot a^t$
$t...$ Period of time
$a ...$ Growth factor
$N(t) ...$ Value in dependence on $t$
$N_{0} ...$ Initial amount/start value