What is the partial sum the sum of 3 plus 9i for i equals 3 to 8 ?

Question

parthkohli · Answer

$$\large \rm\sum_{i=3}^{9}3 + 9i$$Do you know some properties of summation?

anonymous · Answer

I'm ok on solving some types of these equations but what throws me off is the i.. I was never taught how to solve when there is an imaginary number

anonymous · Answer

$i$ is not an imaginary number, it is the "index" a dummy variable

parthkohli · Answer

$\rm i$ is not an imaginary number here.

anonymous · Answer

if it makes you feel better, replace $i$ by $k$

parthkohli · Answer

Think: How can you replace a constant with another constant and do iterations?

anonymous · Answer

to solve this wouldn't I use the equations... Sn=n/2(a1+an)  ??

anonymous · Answer

you have few enough terms you can add

anonymous · Answer

but i guess you can use that, i never know the formulas, 
be careful however, since you are starting at $i=3$ and not $i=1$