Question

Need help with sequences. Find the eighth term of the sequence 5,-15,45,-135...

Answer 1

the answer is -10,935

multiply -3 to each term to get the next one.

Answer 2

a1    a2    a3    a4    .........a8

5    -15     45   -135  .........n

a2/a1=-3

a3/a2=45/-15=-3

a4/a3=-135/45=-3

r=-3

finito generale:

progressione geometrica

$a_{n}=a_{1}*r^{n-1}\\ \\a_{n}=5*-3^{n-1}$

sostituiamo n ----> 8

$a_{8}=5*-3^{8-1}\\ \\ \\a_{8}=5*-3^{7}\\ \\ \\a_{8}=5*-2187\\ \\ \\a_{8}=-10935$

the eighth term of the succession is:

-10935

greetings from Italy