sequences and series

1. determine whether the sequence converges or diverges. if it converges, find the limit:

a sub n= (-3)^n / n!

2. show that the sequence defined by

a sub 1= 2
a sub (n+1) = 1/ (3- a sub n)

satifisfies 0 less than (a sub n) less than or equal to 2 and is decreasing. deduce that the sequence is convergent and find its limit.

3. determine whether the geometric series is convergent or divergent. if it converges, find its sum.

sum (n=1) to inifinty (e^n / 3^(n-1) )

please explain in details!!!
thank you very much!!1