Question

What is the sum of the arithmetic sequence 3, 9, 15..., if there are 26 terms?

Answer 1

First you need to find what are in common with these 3? 9-3 =?
15-9 = ?

Answer 2

Have you tried it or not??

Answer 3

formula fo sum of n terms is

Sn = (n/2)[2a + (n-1)d]

Answer 4

so d=6

Answer 5

a = first term(3), d = common difference (6), n = 26

Answer 6

mk hold on...

Answer 7

Formula for Sum is:

\[\large Sum = \frac{n}{2}(2a + (n-1)d)\]

n= 26, a = 3 and d = 6

Now put these in the formula and find the Sum..

Answer 8

yup yup

Answer 9

153

Answer 10

????

Answer 11

ohhhhh wait...

Answer 12

I got something different.

Answer 13

i know hold onnnnnnnnnn lol

Answer 14

I am holding... Would you like elevator music? :)

Answer 15

Check your solution once again..

Answer 16

mk i got 312 now..

Answer 17

No you are incorrect now..
Show me how you are doing it..

Answer 18

Not very nice @KonradZuse :P

Answer 19

:(? I was going to entertain you.

Answer 20

gooooodnessssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss

Answer 21

Shall we do this in steps?

Answer 22

nah i gtg im on a time limit lol i gt leave at 10:00 to get to school on time so i gtg

Answer 23

ok.

Answer 24

http://www.wolframalpha.com/input/?i=26%2F2+%286%2B%2825%29+*+6%29 is what I got.

Answer 25

goodluck.