Question

If the nth term of a sequence is 28-3n what is the 7th term?

Answer 1

Erms.
For 3, 9, 27, ... the common ratio is 3 because:
3 X 3 = 9
9 X 3 = 27
So to find the 7th term you can do it two ways:
One way:
3 is the 1st term, 9 is the 2nd term, 27 is the 3rd term so then
4th term: 27 X 3 = 81
5th term: 81 X 3 = 243
6th term: 243 X 3 = 729
7th term: 729 X 3 = 2,187
Another way:
You can use the explicit formula
a
n
=
a
1
⋅
r
n
−
1
, where
a
n
is the nth term,
a
1
is the first term, n is the number of the term, and r is the common ratio
so
a
7
=
3
⋅
3
7
−
1

a
7
=
3
⋅
3
6

a
7
=
3
⋅
729

a
7
=
2
,
187

Both ways get you to the same answer that the 7th term in that geometric sequence is 2, 187 .

Answer 2

Answer:

7

Step-by-step explanation:

28-3(7)