Question

Помогите пожалуйста.

Answer 1

1)
$S_n={b_1(1-q^n)over1-q},qneq1\\S_8={b_1(1-{1over2^8})over1.5}={1over8}\b_1*{255over256}={3over16}\\b_1={16over85}$

2)
$b_4=b_1q^3\b_1={1over24}*(-8)=-{1over3}\\S_6={b_1(1-q^6)over1-q}=-{1over3}{63over64}{2over3}=-{7over32}$