Question 11: -18,A1,A2.A3,4 are in A.P. find 'd' (a)-11/2 (b)2/11 (c) 11/2 (d)none of these
Answers
Answered by
0
Answer:
Given
a
1
+a
2
+a
3
+...+a
q
a
1
+a
2
+a
3
+...+a
p
=
q
2
p
2
⇒
2
q
[2a
1
+(q−1)d]
2
p
[2a
1
+(p−1)d]
=
q
2
p
2
⇒
2a
1
+(q−1)d
2a
1
+(p−1)d
=
q
p
⇒2a
1
q+(p−1)qd=2a
1
p+(q−1)pd
⇒2a
1
(p−q)=(pq−q−qp+p)d
⇒d=2a
1
So,
a
21
a
6
=
a
1
+20d
a
1
+5d
=
a
1
+40a
1
a
1
+10a
1
=
41a
1
11a
1
=
41
11
Answered by
0
Answer:
(c)11/2 hope helping you
Similar questions