Question

What is the sum of a 17-term arithmetic sequence where the first term is 7 and the last term is -105?

Answer 1

formula is
\[s _{n}=\frac{n}{2}(a _{1}+a _{n})\]

Answer 2

use n=17
a1=7
an=-105

Answer 3

let me know what you got ?

Answer 4

\[\Large s _{17}=\frac{17}{2}(7+(-105))\]

Answer 5

uhhh.... okay. so, n=12. s12 = 12/2 (or 6) times (7-105) ?

Answer 6

oh wait. n is 17??

Answer 7

dyslexia.. i could have sworn that said 12 :( so, 17/2 = 8.5 times -98?

Answer 8

yes

Answer 9

-833 ?

Answer 10

yes

Answer 11

THANKS :D

Answer 12

yw:)