Question

Дано: b1= - 1 1/3
bn+1= -3bn

Найдите b7

Answer 1

$b_{1}=-1\frac{1}{3}\\\\b_{n+1}=-3b_{n}\\\\b_{1+1}=3b_{1}\\\\b_{2}=3b_{1}=3*(-1\frac{1}{3})=3*(-\frac{4}{3})=-4\\\\b_{2}=b_{1}*q\\\\q=\frac{b_{2} }{b_{1}}=-4:(-1\frac{1}{3})=-4*(-\frac{3}{4})=3\\\\b_{7}=b_{1}*q^{6}=-1\frac{1}{3}*3^{6}=-\frac{4}{3}*3^{6}=-972$