S₅ = b₁(1 - q⁵)/(1 - q), де q = b₂/b₁ = 4/8 = 0,5.
Отже, S₅ = 8(1 - 1/32)/(1 - 1/2) = (8 - 1/4)/(1/2) =16 - 1/2 = 15,5
S₅ = b₁(1 - q⁵)/(1 - q), де q = b₂/b₁ = 4/8 = 0,5.
Отже, S₅ = 8(1 - 1/32)/(1 - 1/2) = (8 - 1/4)/(1/2) =16 - 1/2 = 15,5