Question

Помогите пожалуйста)

Answer 1

$b_{2}=0,04\\\\b_{4}=0,16\\\\q^{2}=\frac{b_{4} }{b_{2}}=\frac{0,16}{0,04}=4\\\\q_{1}=-2\\\\q_{2}=2\\\\b_{1}'=\frac{b_{2}}{q_{1}}=\frac{0,04}{-2}=-0,02\\\\b_{1}''=\frac{b_{2} }{q_{2}} =\frac{0,04}{2}=0,02$

$S_{9}=\frac{b_{1}(q^{9}-1)}{q-1}=\frac{0,02(2^{9}-1)}{2-1}=0,02*511=10,22$

$5)q=3\\\\S_{4}=560\\\\S_{4}=\frac{b_{1}*(q^{4}-1)}{q-1}\\\\560=\frac{b_{1}(3^{4}-1)}{3-1}\\\\1120=b_{1}*80\\\\b_{1}=\frac{1120}{80}=14$