(Q4).Find which of the following are not G.P.
(iv)-4, -20, -100, -500, ……
Given: -4, -20, – 100, -500, ……
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