Question

I could someone explain to me how to solve this (20 sigma notation I=1) 2i

Answer 1

\[\sum_{i=1}^{20}2i\]?

Answer 2

Yes

Answer 3

Do I factor 2 out of the sum

Answer 4

First??

Answer 5

What this is saying is you add up 2i for i from 1 to 20:
2(1) +2(2) +...+2(19)+2(20)
There are two ways to do this:
The long way is to add them up...

The short way is to use the formula:
\[s=\frac{ n(a_1+a_n) }{ 2 }\]
Where n is the number of terms, a1 is the first term, and a2 is the last term.

Answer 6

Don't worry about factoring the 2 out, the equation doesn't depend on the distance between the numbers.

Answer 7

Okay so would I then multiply 2 with n and I with n(n+1)/2

Answer 8

*i

Answer 9

n is the number of terms (20), a1 is the first term (2×1=2), an is the last term (2×20=40)

Answer 10

Oky thank you I got the answer 240 wen I solved it

Answer 11

*420