having a bit of trouble working through sigma notation in first year calc. I get the basic principles at work here, but when the stopping point is a variable, like n, I don't really know how to simplify. Couldn't find answers elsewhere because I didn't quite know how to articulate my question!

So this is the question I'm working with, says to find the value of the sum.

$$\sum_{i=1}^n (3 + 6i)^2$$

How would I evaluate this and then notate my answer? Cheers!

• Do you know formulas for a) $1+2+\cdots+n$, and b) $1^2+2^2+\cdots+n^2$? – angryavian Nov 29 '17 at 7:28
• Yep, I know that much. It's really more a question of applying them together here? – Avi Nov 29 '17 at 7:29

The final answer is in terms of $n$.