Which of the following are exponential functions? Select all correct answers.
Select all that apply:

f
(
x
)
=
3
(
9
)
x

g
(
x
)
=
3
(
−
1
2
)
x

h
(
x
)
=
9
(
4.76
)
x

j
(
x
)
=
12
(
1
7
)
x

k
(
x
)
=
6
(
−
5.4
)
x