10)
[tex]\it \dfrac{b_1}{b_3}=\dfrac{1}{16} \Rightarrow \dfrac{b_1}{b_1q^2} = \dfrac{1}{16} \Rightarrow \dfrac{1}{q^2} = \dfrac{1}{16} \Rightarrow q^2=16 \Rightarrow q = \pm4[/tex]
[tex]\it b_1=\dfrac{b_2}{q} =\dfrac{8}{\pm4} =\pm2[/tex]
11)
[tex]\it b_1=729=3^6
\\ \\
b_9=b_1\cdot q^8 = 3^6\cdot\dfrac{1}{3^8} =\dfrac{1}{3^2} =\dfrac{1}{9}[/tex]
9)
[tex]\it b_2=4=2^2
\\ \\ \\
b_6=b_2\cdot q^4 = b_2\cdot \left(\dfrac{b_2}{b_1}\right)^4 = \dfrac{b_2^5}{b_1^4}=\dfrac{2^{10}}{2^4} =2^6=64[/tex]
