Answer
A recursive rule for the sequence is
$a_1=-2.5,a_n=4\cdot a_{n-1}$
Work Step by Step
The given explicit rule is
$a_n=-2.5(4)^{n-1}$
First term is
$a_1=-2.5$
Common ratio is
$r=4$
Recursive equation for a geometric sequence.
$a_n=r\cdot a_{n-1}$
Substitute $4$ for $d$.
$a_n=4\cdot a_{n-1}$
Hence, a recursive rule for the sequence is
$a_1=-2.5,a_n=4\cdot a_{n-1}$
