Question

The first term of an arithmetic sequence is –12 and the ninth

term is 16.
Calculate the value of the common difference.

Answer 1

d =
`(7)/(2)`

Explanation:

The nth term of an arithmetic sequence is

`a_(n)` = a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Given a₉ = 16 , then

- 12 + 8d = 16 ( add 12 to both sides )

8d = 28 ( divide both sides by 8 )

d =
`(28)/(8)` =
`(7)/(2)`