geometric progression

a geometric progression is a sequence of the form
[cite:;taken from @discrete_kenneth_2018 chapter 2.4 sequences and summations; definition 2]
the formula for the th number in a geometric sequence with initial value and common ratio is:
if and are real numbers and , then
[cite:;taken from @discrete_kenneth_2018 chapter 2.4.5 summations; theorem 1]
the sum of an infinite geometric sequence where is the first term and is the common ratio is