Advertisements
Advertisements
Question
If the sum of n terms of an A.P. be 3n2 + n and its common difference is 6, then its first term is ______.
Options
2
3
1
4
Solution
If the sum of n terms of an A.P. be 3n2 + n and its common difference is 6, then its first term is 4.
Explanation:
In the given problem, the sum of n terms of an A.P. is given by the expression,
Sn = 3n2 + n
Here, we can find the first term by substituting n = 1 as sum of first term of the A.P. will be the same as the first term. So we get,
Sn = 3n2 + n
S1 = 3 (1)2 + (1)
= 3 + 1
= 4
Therefore, the first term of this A.P is a = 4.
RELATED QUESTIONS
The sum of three numbers in A.P. is –3, and their product is 8. Find the numbers
Is -150 a term of the AP 11, 8, 5, 2, ……?
If ` 4/5 ` , a , 2 are in AP, find the value of a.
Find the sum of all multiples of 9 lying between 300 and 700.
The nth term of an AP is given by (−4n + 15). Find the sum of first 20 terms of this AP?
Write the value of a30 − a10 for the A.P. 4, 9, 14, 19, ....
If an = 3 – 4n, show that a1, a2, a3,... form an AP. Also find S20.
In an A.P. sum of three consecutive terms is 27 and their products is 504. Find the terms. (Assume that three consecutive terms in an A.P. are a – d, a, a + d.)
Solve the equation
– 4 + (–1) + 2 + ... + x = 437
If the first term of an A.P. is p, second term is q and last term is r, then show that sum of all terms is `(q + r - 2p) xx ((p + r))/(2(q - p))`.
