Question

Find the missing term of the following arithmetic sequence

-45 ___ -12

-33
-19.5
-28.5
-21

Answer 1

a₂ = - 28.5

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

here a₁ = - 45 and given a₃ = - 12 , then

a₁ + 2d = - 12 , that is

- 45 + 2d = - 12 ( add 45 to both sides )

2d = 33 ( divide both sides by 2 )

d = 16.5

Then

a₂ = a₁ + d = - 45 + 16.5 = - 28.5