Question

How do you express the series `4+8+12+16+20+24` using sigma notation?

Answer 1

`S_n=Sigma_(r=1)^(r=n)(t_r)=Sigma_(r=1)^(r=n)(4r)`

Explanation:

By inspection it is revealed that the series given is an AP with first term a=4 and common difference b = 4
So general rth term is given by `t_r=4+(r-1)4=4r`
Hence the sum of the series up to nth term can be written as
`S_n=Sigma_(r=1)^(r=n)(t_r)=Sigma_(r=1)^(r=n)(4r)`