Answer
$\sum_{i=1}^{14}(2i+3)$
Work Step by Step
Since, we have $5+7+9+11+.....31$
This form an arithmetic progression sequence whose first term is $5$ and last term is $31$ with common difference of $2$.
For an arithmetic progression sequence, we have
$a_n=a_1+(n-1)d$
thus, $a_n=5+(n-1)2=5+2n-2=2n+3$
when $n=14$
Lat term becomes $a_{14}=2(14)+3=31$
Hence, $5+7+9+11+.....31$can be summed up with the summation notation as:
$\sum_{i=1}^{14}(2i+3)$
