Question

Find the indicated sum for the following arithmetic series: S18 for 2+9+16+23.....(must show work)

Answer 1

Do you know the arithmetic series sum formula?

Answer 2

I forgot it.

Answer 3

You should look it up so you won't forget easily !

Answer 4

Ok... give me a second....

Answer 5

Sn=n(a1+an)/2
\[S _{n}=n(a _{1}+a _{n})\div2\]

Answer 6

Do you know formula for a_n?

Answer 7

\[a _{n}=a _{1}+(n-1)d\]

Answer 8

So its 2+(18-1)7

Answer 9

Or 121

Answer 10

yeeeh, you figure it out by yourself :D

Answer 11

How about Sn?

Answer 12

Is it 1107?

Answer 13

18(2+121)/2

Answer 14

yep, 9* 123!

Answer 15

All you do is to give yourself more credit ;)

Answer 16

Thanks so much!!!!

Answer 17

Remember, without memorize the formula, nobody can help you!

Answer 18

Of course, it's easily for me to work it out! but I'd be happier if you success in the future w/o my help ;)