Question

what is the sum of the sereis. I dont know what to do??

Answer 1

Given:

$\sum ^{24}_{c\mathop=1}(155-3c)$

Let's evaluate the expression.

Apply the formula for summation of a conatant:

$\sum ^n_{k=1}c=cn$

Split the summation into smaller summations using summation rules:

$\sum ^{24}_{c=1}155-3\sum ^{24}_{c=1}c$

Apply the formula:

$undefined$

Solving further:

$(155\ast24)-(-3\cdot\frac{24(24+1)}{2})$$\begin{gathered} (3720)+(-3\cdot\frac{24(25)}{2}) \\ \\ (3720)+(-3\cdot\frac{600}{2}) \\ \\ (3720)+(-3\cdot300) \\ \\ 3720+(-900) \\ \\ 3720-900=2820 \end{gathered}$

ANSWER:

2820