# Infinite Geometric series simple question

• Apr 13th 2013, 12:11 PM
vaironxxrd
Infinite Geometric series simple question
Hello guys,

I'm having problems with entering an answer on my current homework problem. My course is online and it's asking me

For what values of the common ratio r is it possible to find the sum of an infinite geometric series? (Enter your answer using interval notation.)?

I tried using (-1,1) because |r| < 1 , but it appears as a wrong answer (Headbang) I'm a wrong here?

r could be between -1 and 1
• Apr 13th 2013, 12:30 PM
Plato
Re: Infinite Geometric series simple question
Quote:

Originally Posted by vaironxxrd

I'm having problems with entering an answer on my current homework problem. My course is online and it's asking me

For what values of the common ratio r is it possible to find the sum of an infinite geometric series? (Enter your answer using interval notation.)?
I tried using (-1,1) because |r| < 1 , but it appears as a wrong answer, I'm a wrong here?
r could be between -1 and 1

What is the series or question?
• Apr 13th 2013, 12:36 PM
vaironxxrd
Re: Infinite Geometric series simple question
Quote:

Originally Posted by Plato
What is the series or question?

That was the question: For what values of the common ratio r is it possible to find the sum of an infinite geometric series? (Enter your answer using interval notation.)

But I found out the answer was: (-1,0)U(0,1)
• Apr 13th 2013, 04:27 PM
Prove It
Re: Infinite Geometric series simple question
Surely the series a + 0 + 0 + 0 + 0 + ... is convergent (to a), and this is a geometric series with r = 0... So the answer SHOULD be (-1, 1).
• Apr 13th 2013, 04:47 PM
Plato
Re: Infinite Geometric series simple question
Quote:

Originally Posted by Prove It
Surely the series a + 0 + 0 + 0 + 0 + ... is convergent (to a), and this is a geometric series with r = 0... So the answer SHOULD be (-1, 1).

That is exactly right. But realize that this is an online quiz-program.
As such, there is no accounting for the quirks.
Only the programmer knows why he/she thinks that answer is correct even though it is not.

Online courses appear to be the future of education.

If that is correct, we are doomed. In most cases, programmers are not good instructors.
• Apr 16th 2013, 01:30 AM