Question

how many terms of the sequence 18,16,14 ,,... should be taken so that their sum is zero

Answer 1

12,10,8,6,4,0

I hope this answer is right

Answer 2

Answer:

19 terms were required to make the sum zero.

Step-by-step explanation:

Given : The sequence 18,16,14.

To find : How many terms of the sequence should be taken so that their sum is zero?

Solution :

The sequence is an AP = 18 , 16 , 14 .....

Where, First term (a) = 18

Common Difference (d) = 16-18 = -2

$S_n = 0$

The formula of sum of sequence is

$S_n=\frac{n}{2}[2a+(n-1)d]$

$0=\frac{n}{2}[2(18)+(n-1)(-2)]$

$0=n[36-2n+2]$

$0=n[38-2n]$

$\text{Either }n=0 \text{ or }38-2n=0$

n=0 cannot be possible.

So, $2n=38$

$n=19$

Therefore, 19 terms were required to make the sum zero.