Question

find the nth term if the sum of n terms is given by
S_n = n^2 + n + 1

Answer 1

find sum upto n-1 terms , i.e, fin \[S_{n-1}\]
then n'th term = \[S{n}-S_{n-1}\]

Answer 2

well i've tried that already
that doesnt work here,
the constant term is causing problems

Answer 3

means you have answer and your work doesn't match with answer given ?

Answer 4

i dont have the answer.

Answer 5

and the answer which comes out from this method, if you cross check it by putting different values of n, doesnt satisfy.

Answer 6

okk...show your work...

Answer 7

why dont you give it a try, am quite sure the method wont work.

Answer 8

okay.

Answer 9

Sn = n^2 + n + 1
Sn-1 = (n-1)^2 + n

Sn -Sn-1 = an = n^2 +1 - (n-1)^2

now lets check :
a1 = 2
but
S1 = 3

contradiction ..

Answer 10

yes, even i got n'th term =2n
is this arithmetic series ?

Answer 11

i dont know what series is this, my teacher asked me this, she couldnt solve it herself.

Answer 12

i tried another way also, here is where i got stuck :
Sn=n^2 + n +1
=n(n+1) +1
=2 summation(n) + 1

had 1 not been there, answer would have been 2n, but the constant is causing problems.

Answer 13

only if we knew summation of what sequence/series =1 ..can we figure that out ?

Answer 14

i mean
summation upto n terms of what sequence/series =1 ?

Answer 15

i can think of one such infinite series, but i don't think that will be expected here....
0.5+0.25+0.125+... =1

Answer 16

n should be taking any values/natural number.
yours is a particular case of n->inf

Answer 17

@ParthKohli @shubhamsrg @mukushla

Answer 18

ohh,,damn clicked closed where i had to click bump ! >.<
am i allowed to reopen ?

Answer 19

the question* ?

Answer 20

hmm,,guess i'll reask the question.

Answer 21

here..
http://openstudy.com/study#/updates/50ee7e29e4b07cd2b649a374