Question

Determine o somatorio dos 50 primeiros termos, dada a pa 2,5,...

Answer 1

$\Large\boxed{\begin{array}{l}\sf (2,5,\dotsc)\\\sf r=5-2=3\\\sf a_{50}=a_2+48r\\\sf a_{50}=5+48\cdot3\\\sf a_{50}=5+144\\\sf a_{50}=149\\\sf S_{50}=\dfrac{\diagdown\!\!\!\!\!\!5\!0\cdot (2+149)}{\diagdown\!\!\!\!2}\\\\\sf S_{50}=25\cdot151\\\sf S_{50}=3775\end{array}}$