(Q3).Find the sum of indicated number of terms in each of the following A.Ps.
(iii) -1,
1
4
,
3
2
…… ;10 terms.
Given: -1,
1
4
,
3
2
…… ;S
10
.
a = –
d = t2 – t1 =
1
– (-
) =
+
1
=
⇒ S
n
=
n
2
[2×a + (n-1)d]
⇒ S
10
=
2
[2×(-
) + (
-1)×(
)]
=
[-
+
×
] =
[-
+
]
=
[
-
+
] =
×
=
=
Clear