Помощ за задача 5

[Гост]

Как се решава?

[ammornil]

[tex]\div a_{1}, a_{2}... a_{n}[/tex]
[tex]a_{n}=a_{1}+(n-1)d[/tex]

[tex]\begin{array}{|l} a_{4} +a_{5} = 29 \\ a_{3} -a_{1} = 6 \end{array} \Leftrightarrow \begin{array}{|l} a_{1}+3d+a_{1}+4d = 29 \\ a_{1}+2d -a_{1} = 6 \end{array} \Leftrightarrow \begin{array}{|l} 2a_{1}+7d= 29 \\ d=3 \end{array} \Leftrightarrow \begin{array}{|l} 2a_{1}= 8 \\ d=3 \end{array} \Leftrightarrow \begin{array}{|l} a_{1}=4 \\ d=3 \end{array}[/tex]

[tex]a_{2}=a_{1}+d=4+3=7[/tex]