Question

How many terms of the AP : 15,12,9.....should be taken so that their sum is zero?

Answer 1

Step-by-step explanation:

a=15

d=a2-a1

d=12-15

d=-3

an=a+(n-1)d

0=15+(n-1)-3

0=15-3n+3

-15=-3n+3

-15-3=-3n

-18=-3n

18=3n

18/3=n

6=n

n=6

Answer 2

11 terms should be taken if you want the sum to be 0