Question

What is the sum of the first seven terms of the geometric series 3 − 6 + 12 − . . . ?

Answer 1

see its a Infinite Geometric Series.....
a_1 = 3
r = -2

Answer 2

Ya, im just trying to find the 7th term.

Answer 3

so like s7=?

Answer 4

in a geomtric series
\[a_n = a_1 r^{n-1}\]

and \[S_n =a_1\frac{ 1 - r^n }{ 1-r }\]

Answer 5

so u want to find the sum of first 7 terms

Answer 6

yes

Answer 7

okkk it means
\[S_7 = 3(\frac{ 1 - (-2)^7 }{ 1 - (-2) })\]

Answer 8

oh alright let me plug that in

Answer 9

go on nd solve S_7

Answer 10

Ok thank you for your help!

Answer 11

u welcome :)