Answer
An exponential function is of the form $y=ab^x$, where $a$ and $b$ are real, non-zero numbers. Exponential functions do not need to account for a term number (unlike geometric sequences).
Work Step by Step
A geometric sequence is of the form $y=ar^{x-1}$, where $a$ and $r$ are real, non-zero numbers. An exponential function could be used to describe a geometric sequence.
Assume $a, b, x,$ and $y$ are real, non-zero numbers.
$y=ab^x$
$y/b=ab^x/b$
$y/b = ab^{x-1}$