q=\frac{b_3}{b_2}=\frac{0.16}{0.04}=4\\\\ b_1=\frac{b_2}{q}=0.01;\\ S_n=b_1\frac{1-q^{n}}{1-q};=> \ S_9=b_1\frac{1-q^{9}}{1-q}=0.01\frac{1-4^{9}}{1-4}=\\\\ =0.01\frac{1-262144}{-3}=0.01\frac{-262143}{-3}=0.01\cdot 87381=873.81" alt="b_1, b_2=b_1q,\ b_3=b_2q\ =>q=\frac{b_3}{b_2}=\frac{0.16}{0.04}=4\\\\ b_1=\frac{b_2}{q}=0.01;\\ S_n=b_1\frac{1-q^{n}}{1-q};=> \ S_9=b_1\frac{1-q^{9}}{1-q}=0.01\frac{1-4^{9}}{1-4}=\\\\ =0.01\frac{1-262144}{-3}=0.01\frac{-262143}{-3}=0.01\cdot 87381=873.81" align="absmiddle" class="latex-formula">