Hi

The denominator is power of 3

The numerator increases by 3 each time

Each fraction is therefore like

The numerator increases by 2 therefore is like 2n+c

The numerator increases by 3 therefore is like 3n+c'

For n=0, 2n+c=1 and 3n+c'=4 lead to c=1 and c'=4

Each fraction is like