Question

The first four terms of an arithmetic sequence are 28, 20, 12, and 4. Which term of the sequence is -36?

Answer 1

9th term in the given sequence is -36.

Explanation:

Here the first four terms of the sequence is 28, 20 , 12 and 4

Now, a2 -a1 = 20 - 28 = -8

a3 - a2 = 12- 20 = -8

⇒ Here, d = - 8 , a = 28

Now, n th term in an AP :
`a_n = a+ (n-1)d`

Here a(n) = -36

⇒ -36 = 28 + (n-1)(-8)

or, -36 = 28 - 8n +8

or, 8n = 28 + 8 + 36 = 72

or, n = 72/8 = 9

⇒ n = 9

Hence, the 9th term in the given sequence is -36.