Question

в12=128, в15= 1024

q-? в6-? S6-? 

Answer 1

b12=b1q^11, b1=b12/q^11,

b15=b1q^14, b15=b12q^3, q^3=b12/b12,

q^3=1024/128,

q^3=8,

q=2.

b1=128/2^11=1/16.

b6=b1q^5,

b6=1/16 * 2^5=32/16=2.

S6=b1(1-q^6)/(1-q)=1/16(1-2^6)/(1-2)=63/16=3 15/16.