Для геометрической прогрессии (bn) найдите Sn, если: в) b1 = -4, q = ½; n = 13; г) b1 =...

Question

Для геометрической прогрессии (bn) найдите Sn, если:
в) b1 = -4, q = ½; n = 13;
г) b1 = 4,5, q = 1/3, n = 8.

Answer 1

В) s13 = b1 * (1-q^13)/(1-q) = -4 *(1-1/8192) /(1/2) = -8191*4/(8192*0.5) = -8191/1024 = -8
г) s8 = 4.5 * (1-(1/3)^8)/(2/3) =4.5 * 6560 * 3/ (2 * 6561) = 6.75