Question

sum of the first 7th term is 77 and sum of the first 14th term is 301 find the sum of terms from 8th to 14th terms? find 14th term?find 11th term? what is the sum of the 1st and 14th term

Answer 1

Step-by-step explanation:

Sn=n/2[2a+(n-1)d]

Given that

sum of the first 7th term is 77 --

n=7

So, S7= n/2[2a+(n-1)d]

77=7/2[2a+(7-1)d]

77×2/7=2a+6d

2a+6d=22---A

sum of the first 14th term is 301

So,S14 = 2a+13d=43---B

From A and B we justify that

d = 3

From A,

2a+6d =22

2a+6×3=22

2a=22-18

a=4/2

a=2