Question

the sum of n terms is given by sn=3n2+n write first 3 terms of an ap
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Answer 1

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.

Answer 2

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