Question 1026794
(a)  The sum of the first six terms of a GP is given by {{{S[6] = g[1]((r^6-1)/(r-1))}}}
Since r = 5, the {{{S[6] = g[1]((5^6-1)/(5-1)) = 3906g[1] = 2604}}}

==> {{{g[1] = 2/3}}}, the first term of the GP.

(b)  2/3, 10/3, 50/3, 250/3, 1250/3, 6250/3.