Question

Find the 18th term in the following
arithmetic sequence:
-2, -6, -10, -14, . . .

Answer 1

Answer: -70

Explanation:

{
`a_(n)`=
`a_(1)`+(n-1)d}

a_{1}= -2

d= -4

`a_(18) =-2+(18-1)*(-4)=-2-68 = -70`

Answer 2

-70

Explanation:

-2, -6, -10, -14, ...

-6 - (-2) = -4

The common difference in -4.

The nth term of an arithmetic sequence with common difference d is

a_n = a_1 + d(n - 1)

For n = 18,

a_18 = -2 + (-4)(18 - 1)

a_18 = -2 + (-4)(17)

a_18 = -2 - 68

a_18 = -70