Help with this question I need to use geometric series
Let S be the set of all real numbers of the form
a1/3 + a2/3^2 + a3/3^3 + ....
where a_i is equal to either 1 or 0 or 2 for each i
(a) Is the number 1/7 in the set S?
(b) Is the number 1/4 in the set S?
