Question

найдите сумму первых восьми членов геометрической прогрессии -3,6,-12

Answer 1

b1 = -3
q = -2
n = 8
S = (b1*(q^n - 1))/(q -1) = (-3*((-2)^8 -1))/(-2 - 1) = 255

Answer 2

b 1 = -3    q = -2    n = 8
S = (b1*(q^n - 1))/(q -1) = (-3*((-2)^8 -1))/(-2 - 1) = 255