# If k+1,2k-1 and 3k+1 are three consecutive numbers of a geometric progression what is the possible answers for common ratio.

*print*Print*list*Cite

Expert Answers

jeew-m | Certified Educator

By the three numbers we can derive the common ratio(r) as;

`r = (2k-1)/(k+1) = (3k+1)/(2k-1)`

`(2k-1)/(k+1) = (3k+1)/(2k-1)`

`(2k-1)(2k-1) = (3k+1)(k+1)`

`4k^2-4k+1 = 3k^2+4k+1`

`k^2-8k = 0`

`k(k-8) = 0`

When k = 0 then r `=(2xx0-1)/(0+1) = -1`

When k = 8 then r `= (2xx8-1)/(8+1) = 15/9 = 5/3`

*So the possible values for common ratio is -1 or 5/3.*

Further Reading: