Question

How do you write a rule for the nth term of the arithmetic sequence given d=-3, `a_2=18`?

Answer 1

`a_n=24-3n`

Explanation:

`"the nth term of an arithmetic sequence is"`

`•color(white)(x)a_n=a+(n-1)d`

`"where a is the first term and d the common difference"`

`"we have to find a"`

`a_2=a+d=18`

`rArra-3=18rArra=21`

`rArra_n=21-3(n-1)`

`color(white)(rArra_n)=21-3n+3`

`rArra_n=24-3n`