Which of the following is the recursive definition for the geometric sequence $81,-27,9,-3,\dots$?

Consider the geometric sequence where $u_2=10$ and $u_5=80$. Find the common ratio $r$.

A sequence is defined recursively by $u_{n+1}=\frac{2}{3}{u}_n$ with $u_1=27$. What is the explicit formula for $u_n$?

A population of bacteria doubles in size every $4$ hours. If the initial population is $P_0$, which expression represents the population after $24$ hours?

Consider a geometric sequence where $u_1=-4$ and $r=0.5$. Which of the following is true regarding the behavior of the terms as $n$ increases?