Question

Нескінченна геометрична прогресія
1) 1; -1/2; 1/4; -1/8

Answer 1

$b_{1}=1\\\\b_{2}=-\frac{1}{2}\\\\q=\frac{b_{2} }{b_{1} }=-\frac{1}{2} :1=-\frac{1}{2}\\\\S=\frac{b_{1} }{1-q}=\frac{1}{1-(-\frac{1}{2})}=\frac{1}{\frac{3}{2}}=\frac{2}{3}\\\\\boxed{S=\frac{2}{3} }$