Question

How many terms of the sequence -35, -28, -21,..... should be taken so that their sum is zero?

Answer 1

Answer:number of terms to be taken = 11

Step-by-step explanation:

a=-35,d=7 Sn=0,n=?

0=n/2 [2(-35)+(n-1)7]

7n^2-77n=0

n^2 -11n=0

n[n-11]=0

that implies n=11