Advertisements
Advertisements
प्रश्न
The sum of first n terms of an A.P. is 3n2 + 4n. Find the 25th term of this A.P.
Advertisements
उत्तर
We know
\[a_n = S_n - S_{n - 1} \]
\[ \therefore a_n = 3 n^2 + 4n - 3 \left( n - 1 \right)^2 - 4\left( n - 1 \right)\]
\[ \Rightarrow a_n = 6n + 1\]
APPEARS IN
संबंधित प्रश्न
The first and the last terms of an AP are 7 and 49 respectively. If sum of all its terms is 420, find its common difference.
How many multiples of 4 lie between 10 and 250?
If (m + 1)th term of an A.P is twice the (n + 1)th term, prove that (3m + 1)th term is twice the (m + n + 1)th term.
If the 12th term of an A.P. is −13 and the sum of the first four terms is 24, what is the sum of first 10 terms?
Find the value of x for which (x + 2), 2x, ()2x + 3) are three consecutive terms of an AP.
In an A.P. sum of three consecutive terms is 27 and their product is 504, find the terms.
(Assume that three consecutive terms in A.P. are a – d, a, a + d).
Sum of 1 to n natural numbers is 36, then find the value of n.
Let Sn denote the sum of n terms of an A.P. whose first term is a. If the common difference d is given by d = Sn − kSn−1 + Sn−2, then k =
The first and last term of an A.P. are a and l respectively. If S is the sum of all the terms of the A.P. and the common difference is given by \[\frac{l^2 - a^2}{k - (l + a)}\] , then k =
If \[\frac{5 + 9 + 13 + . . . \text{ to n terms} }{7 + 9 + 11 + . . . \text{ to (n + 1) terms}} = \frac{17}{16},\] then n =
Q.2
Find the sum of first 20 terms of an A.P. whose first term is 3 and the last term is 57.
Find the value of x, when in the A.P. given below 2 + 6 + 10 + ... + x = 1800.
How many terms of the A.P. 27, 24, 21, …, should be taken so that their sum is zero?
The middle most term(s) of the AP: -11, -7, -3,.... 49 is ______.
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is ______.
Find the sum:
`4 - 1/n + 4 - 2/n + 4 - 3/n + ...` upto n terms
Find the middle term of the AP. 95, 86, 77, ........, – 247.
The 5th term and the 9th term of an Arithmetic Progression are 4 and – 12 respectively.
Find:
- the first term
- common difference
- sum of 16 terms of the AP.
The nth term of an A.P. is 6n + 4. The sum of its first 2 terms is ______.
