# Calculate the X-cordinate for any number in a geometric progression

• Feb 8th 2010, 09:09 PM
vbinteface
Calculate the X-cordinate for any number in a geometric progression
Hi.

If I have series of 1,2,4,7,11 on X-axis with co-ordinates 0,1,2,3,4 respectively, can I calculate the X-coordinate for any number in the series in one "generalized equation" ?
For example the number 7 in the progression series is located at x=3.
So, if given the number 11, how can it's corresponding x-coordinate be calculated using a single equation?

• Feb 8th 2010, 09:54 PM
mr fantastic
Quote:

Originally Posted by vbinteface
Hi.

If I have series of 1,2,4,7,11 on X-axis with co-ordinates 0,1,2,3,4 respectively, can I calculate the X-coordinate for any number in the series in one "generalized equation" ?
For example the number 7 in the progression series is located at x=3.
So, if given the number 11, how can it's corresponding x-coordinate be calculated using a single equation?

There is no unique function that will generate that sequence of values. One possible rule can be found by noting that each term is found by adding one more than was added to get the previous term. But other answers are possible (and will all generate a different number that comes after 11 ....)
• Feb 9th 2010, 05:46 PM
vbinteface
Thanks mr. fantastic.
"There is no unique function that will generate that sequence of values"

I think there should be some equations for geometric progressions at least for a finite series.

1) If dx=1 then obviously x=n
2) If dx=2 then x=n/2
3) if dx=geometric progression, the problem arises, and we cannot directly derive the x-coordinate for "any" number as in 1) and 2)

If anyone has worked on equations for geometric progressions involving finite/infinite series, please reply.
• Feb 10th 2010, 03:10 AM
mr fantastic
Quote:

Originally Posted by vbinteface
Thanks mr. fantastic.
"There is no unique function that will generate that sequence of values"

I think there should be some equations for geometric progressions at least for a finite series.

1) If dx=1 then obviously x=n
2) If dx=2 then x=n/2
3) if dx=geometric progression, the problem arises, and we cannot directly derive the x-coordinate for "any" number as in 1) and 2)

If anyone has worked on equations for geometric progressions involving finite/infinite series, please reply.

What you have posted is NOT a geometric progression. Again I say, there is no unique answer.
• Feb 10th 2010, 10:51 PM
vbinteface
Thank you mr. fantastic for your help.