Find the nth term of the following
geometric sequence 1, 5, 25, 125, 625, ...
Then find the 7th term.
| Solve | Step |
|
r = 625 ÷ 125 = 5,
r = 125 ÷ 25 = 5 |
Find
the common ratio r = 5 |
|
an = a1rn - 1 |
Use the formula for geometric sequence. |
|
a1 = 1 and r = 5 |
a1 = 1 is the first term of the sequence. |
|
an = (1)5n - 1 = 5n - 1 |
nth term |
|
a7 = (1)57 - 1 = 57 - 1 = 56 = 15,625 |
7th term |
| Spot Check |
|
a1 = 51 - 1 = 50 = 1 |
|
a3 = 53 - 1 = 52 = 25 |
|
a5 = 55 - 1 = 54 = 615 |