Can someone please help me get this the correct answer is -6026/13
find the sum of K 12-57
57
E(Sum) 7-4k
k=12 13
Would that be:
$\displaystyle
\sum_{k=12}^{57} \frac{7-4k}{13}
$
This is an arithmatic progression with first term $\displaystyle -\ \frac{41}{13}$ (which corresponds to $\displaystyle k=12 $), common difference $\displaystyle -\ \frac{4}{13}$ and with $\displaystyle 57-12+1 = 46$ terms. You should have a forumla for this.
RonL