Question

How to tell if infinite or finite geometric series?

Answer 1

The series is finite if the number of terms or the last term is given. If a summation sign is used, the limit of the summation is infinity for an infinite series.
1 + 2 + 4 + 8 + ... . . . . . is an infinite series. It has no last term.

`=\sum\limits_(n=1)^(\infty) 2^(n-1)`

1 + 2 + 4 + 8 + ... + 1024 . . . . . is a finite series. The last term is given.
The upper limit on the summation symbol is a finite number.

`= \sum\limits_(n=1)^(11) 2^(n-1)`