If $r > 1$, then $a_n \to \infty$; if $0 < r < 1$, then $a_n \to 0$; if $r = 1$, then $a_n = c$ (constant)

If $r > 0$, the sequence is always positive and monotonic

If $r < 0$ and $|r| > 1$, then $|a_n| \to \infty$ and terms alternate in sign

All of the above