Question

Oblicz S5 ciagu geometrycznego, w ktorym a1=4,q=-2/3

Answer 1

 

Odp. .

Answer 2

Sn = a1 * (1 - q^n) / (1 - q)

 

 

S5 = 4 * (1 - (-2/3)^5) / (1 - (-2/3))

S5 = 4 * (1 - (-32/243)) / (1 +2/3)

S5 = 4 * (1 +32/243) / (5/3)

S5 = 4 * 275/243 * 3/5

S5 = 4 * 55/81

S5 = 220/81

S5 = 2 i 58/81