Question

Помогите пожалуйста

Answer 1

Ответ:

$\dfrac{4}{5}\ ,\ \ \dfrac{7}{15}\ ,\ \ \dfrac{10}{45}\ ,\ \ \dfrac{13}{135}\ ,\ ... \ \ \ a_{n}=\dfrac{3n+1}{5\cdot 3^{n-1}}\ ,\ n\in N\\\\\\n=1:\ \ a_1=\dfrac{3\cdot 1+1}{5\cdot 3^0}=\dfrac{4}{5}\\\\\\n=2:\ \ a_2=\dfrac{3\cdot 2+1}{3\cdot 3^1}=\dfrac{7}{15}\\\\\\n=3:\ \ a_3=\dfrac{3\cdot 3+1}{5\cdot 3^2}=\dfrac{10}{45}\\\\\\n=4:\ \ a_4=\dfrac{3\cdot 4+1}{5\cdot 3^3}=\dfrac{13}{135}\\\\.................................................$