Answer:
Two ways to arrive to result:
One way is calculate the 5th term applying definition of geometric sequence:
a
1
=
4
a
2
=
4
⋅
(
−
2
)
=
−
8
a
3
=
(
−
8
)
⋅
(
−
2
)
=
16
a
4
=
16
⋅
(
−
2
)
=
−
32
a
5
=
(
−
32
)
⋅
(
−
2
)
=
64
and so on
Other way is apply general term of a geometric sequence
a
n
=
a
1
⋅
r
n
−
1
For n=5, we have
a
5
=
4
⋅
(
−
2
)
4
=
64
