Use D'Alembert's ratio test to determine the convergent of the following series(hint:Find the general term first)

i)

the general term:

so is it:

is it correct? i don't know how to solve the limit...please help me....

ii)

general term

is it

limit = 1

convergent

iii)

general term :

limit 2

2>1, divergent

please help guide & correct me, all help appreciated..thank you & regards