Ask a Doubt
Request a call back

Join NOW to get access to exclusive study material for best results

CBSE Class 10 Answered

If sum of n terms of an AP is 2n^2+5n, then find its nth term?
Asked by | 27 Dec, 2012, 11:59: PM
answered-by-expert Expert Answer
Sum of first n terms of AP, Sn = 2n2 + 5n
 
Now choose n =1 and put in the above formula,
First term = 2+5 = 7
 
Now put n=2 to get the sum of first two terms = 2x4 + 5x 2= 8 + 10 = 18
 
This means 
 
first term + second term = 18
 
but first term =7 as calculated above
 
so, second term = 18-7 = 11
 
So common difference becomes, 11-7 = 4
 
So the AP becomes, 7, 11, 15, ....
nth term = a + (n - 1)d = 7 + (n-1)4 = 7 + 4n - 4 = 3 + 4n
Answered by | 28 Dec, 2012, 09:41: AM

Application Videos

Concept Videos

Multiple Choice Questions Practice Test
Answered Unanswered My Questions My Answers
CBSE 10 - Maths
1.The mean weight of 9 students is 25 Kg. if one more student is joined in the group, the mean is unaltered. Find the weight of 10th student 2.If the nth term of an A.P is pn+q find its common difference.
Asked by purbashadebnath1980 | 09 Mar, 2024, 12:10: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
find the sum of following 6+13+20+....+97
Asked by deepikaselvam2009 | 20 Feb, 2024, 08:57: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
If the sum of the first n terms of an AP be n and the sum of first n terms be m then sum of its (m+n) terms is -(m+n)
Asked by keshavsinghalhapur | 16 Jan, 2024, 08:46: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
If the sum of first n,2n and 3n terms of an AP be S1 S2andS3 respectively then p3 S2-S1
Asked by keshavsinghalhapur | 15 Jan, 2024, 10:56: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
which term of the AP 3,8,13,18.....is. 78?
Asked by durgauikey7000 | 08 Dec, 2023, 08:16: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
A contract on construction job specifies penalty for delay of completion beyond a certain date as follows Rs. 200 for 1st, Rs. 250 for 2nd, and Rs. 300 for 3rd, so on. If contractor pays Rs. 27,750 as penalty, find the number of days for construction work delayed.
Asked by skandachiranjeevin | 06 Dec, 2023, 07:08: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
5,2,-1....-49 is an arithmetic progression so it has blank terms
Asked by shaikhyakub9946 | 30 Nov, 2023, 11:50: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
The sum of the first 7 terms of an AP is 63 and that of its next 7 terms is 161.find the AP
Asked by prassanna.j | 13 Nov, 2023, 11:24: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
if m times the m th term of an AP is equal to n times the n th term, show that the (m+n) th term of the AP is zero
Asked by prassanna.j | 13 Nov, 2023, 11:23: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Maths
If the pth term of an AP is 1/q and qth term 1/P. Prove that the sum of the first pqth term is 1/2 (pq + 1).
Asked by latayadav23 | 17 Oct, 2023, 08:39: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
My Class Videos Tests ₹ Plans Ask a Doubt
Get Latest Study Material for Academic year 24-25 Click here
×