B1=-3 q=-1/3 b6?b1=-5 q=-2/3 n=5 Sn?

Question

B1=-3 q=-1/3 b6?
b1=-5 q=-2/3 n=5 Sn?

Answer 1

^ - степень
b1=-3 q=-1/3
b6 = b1*q^5 = (-3) *(-1/3)^5 = (-1/3)^4 =1/81

b1=-5 q=-2/3 n=5
Sn = b1*(q^n-1) /(q-1) =(-5)((-2/3)^5-1) / (-2/3 -1) = -275/81 =-3_32/81