Advertisements
Advertisements
प्रश्न
If Sn.., the sum of first n terms of an AP is given by Sn =3n2- 4n, find the nth term.
उत्तर
sn-=3n2 - 4n
Let Sn-1 be sum of (n - 1) terms
tn = Sn - Sn-1
(3n2 - 4n) - [3(n - 1)2- 4(n- 1)]
=(3n2- 4n) - [3n2 - 6n + 3 - 4n+4]
= 3n2 - 4n - 3n2 + 10n- 7
: . tn =6n - 7
Therefore, required nth term =60- 7
APPEARS IN
संबंधित प्रश्न
In the following APs, find the missing term in the box:
`5, square, square, 9 1/2`
Find the 31st term of an A.P. whose 11th term is 38 and the 16th term is 73.
Find the sum of n terms of the series `(4 - 1/n) + (4 - 2/n) + (4 - 3/n)+ ......`
Which term of the A.P. 8, 14, 20, 26, ... will be 72 more than its 41st term?
In an AP, if the common difference (d) = –4, and the seventh term (a7) is 4, then find the first term.
A man saved Rs 16500 in ten years. In each year after the first, he saved Rs 100 more than he did in the preceding year. How much did he save in the first year?
If the nth term of a progression is (4n – 10) show that it is an AP. Find its
(i) first term, (ii) common difference (iii) 16 the term.
Which term of the AP: 92, 88, 84, 80 … is 0?
If 7 times the 7th term of an AP is equal to 11 times its 11th term, then its 18th term will be ______.
Justify whether it is true to say that the following are the nth terms of an AP.
1 + n + n2
