Question

What is the 8th term of the geometric sequence –1, 3, –9, …?

Answer 1

multiply by 3 to get next term
and put -ve sign at odd ones :)

Answer 2

find the commun ratio first

Answer 3

common ratio is -3 right?

Answer 4

\[a _{n}=a _{1}r ^{n-1}\]

Answer 5

right

Answer 6

yess :) it is geomatric and with ratio of -3

Answer 7

so use now the formula i gave above. Insted of r put -3, and instead of n, put 8

Answer 8

and nistead of a0 put 1

Answer 9

sry, instead of a1 put 1

Answer 10

\[a _{8}=-3^{7}\]

Answer 11

wouldnt it be 3^7?

Answer 12

cause the first term is -1 so you have (-1)(-3)^8-1?

Answer 13

ya, right a1=-1

Answer 14

so 3^7 = 2187

Answer 15

thankyou so much!!

Answer 16

yw