Question 1035304
It is given that {{{a[9] = 8a[6]}}}  <==> {{{a[1]*r^8 = 8*a[1]*r^5}}}

==> {{{r^3 = 8}}}  ==> {{{r = 2}}}.

Now from the other given, {{{S[5] = a[1]*((1-2^5)/(1-2)) = 31a[1] = 93}}}

==> {{{a[1] = 3}}}.

==> The general term of this geometric sequence is {{{a[n] =3*2^(n-1)}}}.

The sum of the first twenty terms is {{{S[20] = 3*((1-2^20)/(1-2)) = 3145725}}}