Question

Uma pa (-5,3,...) determine a50, a60 e a30+a20?

Answer 1

$\Large\boxed{\begin{array}{l}\sf (-,5,3,\dotsc)\\\sf r=3-(-5)=3+5=8\\\sf a_{50}= a_2+48r\\\sf a_{50}=3+48\cdot8\\\sf a_{50}=3+384\\\sf a_{50}=387\\\sf a_{60}=a_{50}+10r\\\sf a_{60}=387+10\cdot8\\\sf a_{60}=387+80\\\sf a_{60}=467\end{array}}$

$\Large\boxed{\begin{array}{l}\sf a_{30}+a_{20}=a_2+28r+a_2+18r\\\sf a_{30}+a_{20}=2a_2+46r\\\sf a_{30}+a_{20}=2\cdot3+46\cdot8\\\sf a_{30}+a_{20}=6+368\\\sf a_{30}+a_{20}=374\end{array}}$