the sum of n terms is given by sn=3n2+n write first 3 terms of an ap
Answers
Answered by
0
Answer:
The sum of the first n terms of an AP is given by sn=3n2-n , determine the AP and its 25thterm. The sum of the first n terms of an AP is given by sn=3n2-n , determine the AP and its 25thterm.
Answered by
1
Step-by-step explanation:
Sn = 3n² + n
n/2 {2a+(n-1)d} = n(3n+1)
1/2 {2a+(n-1)d} = 3n + 1
2a + (n-1)d = 6n + 2
a + An = 6n + 2
An = 6n+2-a
A(1) = 8-a
A(2) = 14-a
d = A(2)-A(1)
= 14-a-8+a
d = 6
A(3) = 20-a
a + 2d = 20-a
a + 12 = 20-a
2a = 8
a = 4
प्रथम पद A(1) = 8-4 = 4
द्वितीय पद A(2) = 14-4 = 10
तृतीय पद A(3) = 20-4 = 16
Similar questions