Question

Suppose the sequence {an} is arithmetic with a3 = 15, d = -3/2, and an=6 Find n.

Answer 1

Answer:

The value of n = 9th term

Step-by-step explanation:

Given:

In an arithmetic series

a3 = 15

d = -3/2

an = 6

Find:

The value of n

Computation:

In an arithmetic series

An = a + [n - 1]d

where,

An = last term

a = first term

n = number of term

d = common difference

So,

a3 = a + 2d

15 = a + 2(-3/2)

15 = a - 3

a = 18

An = a + [n - 1]d

6 = 18 + [n - 1][-3/2]

-12 = [n-1][-3/2]

8 = n - 1

The value of n = 9th term