Question

What is the answer to this problem?​

Answer 1

48

Explanation:

It's an arithmetic sequence with common difference d = 7.

`a_1=-8\\\\a_2=-8+7=-1\\\\a_3=-1+7=6\\\\a_4=6+7=13`

Find 9th term.

METHOD 1.

Calculate next terms:

`a_5=13+7=20\\\\a_6=20+7=27\\\\a_7=27+7=34\\\\a_8=34+7=41\\\\a_9=41+7=48`

METHOD 2.

The explicit formula of an arithmetic sequence:

`a_n=a_1+(n-1)d`

Substitue:

`a_n=-8+(n-1)(7)` use the distributive property

`a_n=-8+7n-7\\\\a_n=7n-15`

Put n = 9:

`a_9=7(9)-15=63-15=48`