rewrite each series using sigma notation

Question

9) 1+4+9+16+25+36
and
10) 4+8+12+16+20

Answer 1

You want the general term for each one.
1+4+9+16+25+36
you can easily see that this is the square of the whole numbers, that is n^2

so [sigma] n^2 , from n = 1 to 6
(write n=1 below the "sigma" sign, and 6 on top of it)

for the 2nd, you have an AP
with a = 4, and d = 4
term(n) = a + (n-1)d = 4 + (n-1)(4)
= 4n

I will let you put it together