(Q3).Find which of the following are not G.P.
(iii)1, -1, 1, -1, …..
Given: 1, -1, 1, -1, …….
a
1
= a =
a
2
=
; a
3
=
, a
4
=
a
2
a
1
=
-
= -
;
a
3
a
2
=
-
= -
;
a
4
a
3
=
-
= -
, .....
i.e., r =
a
2
a
1
≠
a
3
a
2
≠
a
4
a
3
= .......... = -
∴ The given list forms a G.P.
Clear