Question

the sum of the first n terms of an ap is given by n square + 8n .find the 12th term of the AP, also find the nth term of the AP

Answer 1

12th term = Sum of 12 terms - Sum of 11 terms

=12^2+8×12- 11^2-8×11

=144+96-121+88

=240-209

=31

a(n)= Sum(n)-Sum(n-1)

Answer 2

hello here is the ans. of your question,

here, S1 = sum of first term

S2 = sum of first two terms of

the a.p.

an = first n term

d = common difference

so, Sn = an= n^2+8

if we put 1 in place of n, so first term will come

a = 8+1 = 9

now, if we put 2 in place of n then S2 will come,

S2 = 20

2nd term of a.p. = S2-S1 = 11

now, d= second term - first term

= 11 - 9 = 2

so, 12th term = a + 11d

= 9 + 22 = 31

an( nth term ) = a + (n-1)d

= 9 + (n-1)2

= 9 + 2n - 2

= 7+2n

hope this will help you

please mark as brainliest please