Question

Найдите сумму бесконечной геометрической прогрессии 56, -28, 14...​

Answer 1

$\displaystyle\bf\\b_{1} =56\\\\b_{2} =-28\\\\b_{2} =b_{1} \cdot q\\\\q=b_{2} :b_{1} =-28:56=-0,5\\\\\\S=\frac{b_{1} }{1-q} =\frac{56}{1-(-0,5)} =\frac{56}{1+0,5}=\frac{56}{1,5} =37\frac{1}{3}\\\\\\Otvet: \ S=37\frac{1}{3}$

Answer 2

b2/b1 = (-28)/56 = (- 0.5)

S = b1/(1-g) = 56/(1-(-0.5) = 56/1,5 = 37.333333 = 37 1/3