Question

Ребята хелп,помогите даю 50 балов (с Дано пишите)

Answer 1

$\displaystyle\bf\\4)\\\\\left \{ {{a_{31}=77 } \atop {a_{22}=-33,7 }} \right. \\\\\\-\left \{ {{a_{1}+30d=77 } \atop {a_{1}+21d=-33,7 }} \right.\\------------\\9d=110,7\\\\\boxed{d=12,3}\\\\a_{1} =77-30d=77-30\cdot 12,3=77-369=-292\\\\\boxed{a_{1} =-292}\\\\\\5)\\\\a_{6} =4\\\\a_{1} +5d=4\\\\\\S_{11} =\frac{2a_{1} +10d}{2} \cdot 11=(a_{1} +5d)\cdot11=4\cdot 11=44\\\\\\\boxed{S_{11} =44}$