Question

Identify the 16th term of a geometric sequence where a1 = 4 and a8 = -8,748.

-172,186,884
-57,395,628
57,395,628
172,186,884

Answer 1

common ratio 7th root of -8748 / 4
= -3
16th root = 4* -3^15 = -57,395,628

Answer 2

its 7th root because a8 / a1 = ar^7 / a = r^7

Answer 3

*a1 r^7 / a1

Answer 4

\[a_n = a_1*r^{n-1} \]\[a_8 = a_1*r^7 \]\[-8,748 = 4*r^7\]\[r^7 = -2187\]\[r=-3\]

Answer 5

\[a_{16}=4*(-3)^{15}\]\[a_{16}=57,395,628\]

Answer 6

Ok this one's correct. Sorry..

Answer 7

haha thank you! i was like wait a minute lol

Answer 8

agh it's negative!
-57,395,628

Answer 9

Something's wrong with my keyboard.. :/

Answer 10

thanks! :]