In 9, the differences between two consecutive terms are
6-3,12-6,24-12...
3,6,12...
Which is not same. So it is not is arithmetic progression .
In 10. the differences are
[tex] 5/6 -0 , 5/3 - 5/6 , 5/2-5/3,... [/tex]
[tex] 5/6,5/3,5/6,.... [/tex]
Which is not same, so it is not in arithmetic progression too .
