Q. 144.0( 4 Votes )

<span lang="EN-US

Answer :

Given: S3 + S8 = 7

S7 + S14 = -3


To find: a10


Formula Used:


Sum of “n” terms of an AP:



Where Sn is the sum of first n terms


nth term of an AP is:


an = a + (n - 1) d


Where an is the last term.


n = no of terms


a = first term


d = common difference


Explanation:


Let the first term and common difference of an AP are a and d, respectively.


a3 + a8 = 7


As we know, nth term of an AP is


an = a + (n - 1) d


where a = first term


an is nth term


d is the common difference


a + 2d + a + 7d = 7


2a + 9d = 7


2a = 7 - 9d [ Eqn 1]


a7 + a14 = - 3


a + 6d + a + 13d = - 3


2a + 19d = - 3


7 - 9d + 19d = - 3 [ using eqn i]


7 + 10d = - 3


10d = - 10


d = - 1


using this value in eqn i


2a = 7 - 9 (- 1 )


2a = 16


a = 8


Now,


a10 = a + 9d


= 8 + 9 (- 1 )


= 8 - 9 = - 1


Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Arithmetic Progression and 'nth' Term of APArithmetic Progression and 'nth' Term of APArithmetic Progression and 'nth' Term of AP55 mins
Sum of n Terms of APSum of n Terms of APSum of n Terms of AP56 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
caricature
view all courses
RELATED QUESTIONS :

Find the indicateKC Sinha - Mathematics

Find the indicateKC Sinha - Mathematics