Question

В геометрической прогрессии (bn)/q = - 2, S5 = 5, 5. Найдите b5.

Answer 1

q=-2, S5=5.5

S5=b1*(q^5-1)/(q-1)=5.5
b1*(-32-1)/(-2-1)=5.5
b1*(-33)/-3=5.5
b1*11=5.5
b1=5.5/11=1/2=0.5
b5=b1*q^4=0.5*16=8