No products in the cart.

If the sum of first 7 …

CBSE, JEE, NEET, CUET

CBSE, JEE, NEET, CUET

Question Bank, Mock Tests, Exam Papers

NCERT Solutions, Sample Papers, Notes, Videos

If the sum of first 7 term of an ap is 49 and that of 17 term is 289 find the sum of first n terms.

Posted by Kashish Bhardwaj 10 months, 2 weeks ago

CBSE > Class 10 > Mathematics

5 answers

Deepanshu Garg 10 months, 2 weeks ago

It's ok bro

Abhinav Raj Singh 10 months, 2 weeks ago

its ok brother

Naman Sisodiya 10 months, 2 weeks ago

Thank

Abhinav Raj Singh 10 months, 2 weeks ago

S7 = 7/2{2a+(n-1)d} => 49= 7/2{2a+(n-1)d} => 14= 2a + (7-1)d =>14 = 2a +6d => a + 3d = 7 ---------------(dividing by 2) => a = 7-3d -----------------(i) for S17:- S17 = 17/2 {2a+(n-1)d} => 289= 17/2 {2a+(17-1)d} => 34 = 2a + 16d => a = 17- 8d ---------------(ii) by eq(i) and eq(ii):- 17 - 8d = 7-3d =>10=5d =>d=2 again by eq(i):- a =1 by Sn:- Sn = n/2 {2a+(n-1)d} =>Sn = n/2{2+(n-1)2} => Sn = n + n^2 - n => Sn = n^2

Abhinav Raj Singh 10 months, 2 weeks ago

n^2

ANSWER

http://mycbseguide.com/examin8/

Related Questions

(A + B )²

Posted by Abhishek Gupta 3 months, 3 weeks ago

CBSE > Class 10 > Mathematics

1 answers

Find cosec 30 degree and cause 60 degree geometrical

Posted by Hari Anand 1 week, 5 days ago

CBSE > Class 10 > Mathematics

0 answers

X-y=5

Posted by Kishan Thakur 1 month, 3 weeks ago

CBSE > Class 10 > Mathematics

1 answers

sin60° cos 30°+ cos60° sin 30°

Posted by Vanshika Bhatnagar 3 months, 3 weeks ago

CBSE > Class 10 > Mathematics

2 answers

Find the sum of the odd no. Between 0 and 50

Posted by Kanika . 2 months ago

CBSE > Class 10 > Mathematics

1 answers

Venu Gopal has twice

Posted by Lakshay Kumar 5 days, 9 hours ago

CBSE > Class 10 > Mathematics

0 answers

Find the nature of quadratic equation x^2 +x -5 =0

Posted by Parinith Gowda Ms 3 months, 3 weeks ago

CBSE > Class 10 > Mathematics

0 answers

Is it possible to design a rectangular mango Grove whose length is twice it's breadth, and the area is 800m²? If so, find it's length and breadth

Posted by Akshata Choukse 3 months, 3 weeks ago

CBSE > Class 10 > Mathematics

0 answers

If 1/2 is a root of equation x^2+kx- 5/4 =0 , then what is the value of k

Posted by Parinith Gowda Ms 3 months, 3 weeks ago

CBSE > Class 10 > Mathematics

1 answers

Water

Posted by S Prajwal 1 week, 5 days ago

CBSE > Class 10 > Mathematics

0 answers

myCBSEguide App

myCBSEguide

Trusted by 1 Crore+ Students

Test Generator

Test Generator

Create papers online. It's FREE.

CUET Mock Tests

CUET Mock Tests

75,000+ questions to practice only on myCBSEguide app

Google Play

Download myCBSEguide App