Найдите формулу n–го члена арифметической прогрессии: b1=-1/27, 2 1/3, bn, 2 2/3, ….

\[b_{1} = - \frac{1}{27},\ \ \ 2\frac{1}{3},\ \ \ b_{n},\ \ \ 2\frac{2}{3},\ldots\]

\[b_{2} = 2\frac{1}{3};\ \ b_{4} = 2\frac{2}{3}:\]

\[b_{3} = \frac{b_{2} + b_{4}}{2} = \frac{2\frac{1}{3} + 2\frac{2}{3}}{2} = \frac{5}{2};\]

\[d = 2\frac{1}{3} + \frac{1}{27} = \frac{7}{3} + \frac{1}{27} =\]

\[= \frac{64}{27} = \frac{64}{27};\]

\[d = \frac{5}{2} - 2\frac{1}{3} = \frac{5}{2} - \frac{7}{3} =\]

\[= \frac{15}{6} - \frac{16}{6} = \frac{1}{6}.\]

\[d \neq d\]

\[Дана\ неверная\ \]

\[последовательность.\]