Q=2,n=7 Sn=635 b1-? b7-?

Question

Q=2,n=7 Sn=635 b1-? b7-?

Answer 1

B1=? b7=? q=2 S7=635 bn=b1*q^(n-1) Sn=b1(q^n-1)/(q-1) S7=b1*(2^7-1)/(2-1) S7=b1*(128-1)=127b1 b1=S7/127=635/127 b1=5 n=7 b7=b1*q^6=5*2^6=5*64 b7=320