Question 255741
The formula for geometric sequences is
(i) {{{Tn = a*r^(n-1)}}}
using given infpormation, we get
(ii) {{{-4 = a*(-1/2)^(1-1)}}}
this is
(iii) {{{-4 = a*(-1/2)^(0)}}}
or
(iv) {{{a = -4}}}
Now, (i) becomes
(v) {{{T(n) = -4(-1/2)^(n-1)}}}
the 8th term is
(vi) {{{T(8) = -4(-1/2)^(8-1)}}}
or
(vii) {{{T(8) = -4(-1/2)^(7)}}}
{{{T(8) = 4/128}}}
T(8) = 1/32