S5=?;b=18;q=1/2 помогите срочно

Question

S5=?;b=18;q=1/2 помогите срочно

Answer 1

S5 = b1*(1-q^5) / (1-q)
S5 = 18*(1- 1\32) / (1-1/2)
Ы5 = 18*(31\32)*2
S5 = 279/8 = 34 7\8 = 34,875