Question

3) Qual é a soma dos termos da PA que obtemos ao inserir 10 termos entre 8 e 118?

Answer 1

$\Large\boxed{\begin{array}{l}\sf Teremos\,12\,termos\,ao\,todo\\\sf os\,termos\,que\,vamos\,inserir\\\sf mais\,os\,n\acute umeros\\\sf 8\,e\,118.\\\sf portanto\\\sf a_1=8\\\sf a_{12}=118\\\sf n=12\\\sf S_{12}=?\end{array}}$

$\Large\boxed{\begin{array}{l}\sf S_{12}=\dfrac{\diagdown\!\!\!\!\!\!12\cdot(8+118)}{\diagdown\!\!\!\!2}\\\\\sf S_{12}=6\cdot126\\\sf S_{12}=756\end{array}}$