it is a geometric sequence
an=a1(r)^(n-1)
a1=first term
r=common ratio
n=which term
first term is 1
common ratio is 5
an=1(5)^(n-1)
that is the equatin/formulf for the nth term
if you want a summation formula of the sequence to the nth term
Sn=\(\frac{a1(1-r^{n})}{1-r}\)
in this case
Sn=\(\frac{1(1-5^{n})}{1-5}\) or
Sn=\(\frac{1-5^{n}}{-4}\)
so in this case
up to 5th term
S5=\(\frac{1-5^{5}}{-4}\)
S5=\(\frac{1-3125}{-4}\)
S5=\(\frac{-3124}{-4}\)
S5=781
anyway
\(a_{n}=(5)^{n-1}\) is the nth term
and
Sn=\(\frac{1-5^{n}}{-4}\) is the summation up to the nth term
