Question

HELP PRECALC GIVING MEDALS AND BECOMING A FAN
1.)Find an explicit rule for the nth term of the sequence.
-4, -8, -16, -32
an = -4 • 2^(n - 1)
an = 2 • -4^(n + 1)
an = 2 • -4^n
an = -4 • 2^n

2.) Find an explicit rule for the nth term of a geometric sequence where the second and fifth terms are -12 and 768, respectively.
an = 3 • (-4)^(n + 1)
an = 3 • 4^(n - 1)
an = 3 • (-4)^(n - 1)
an = 3 • 4^n

Answer 1

HI!!

Answer 2

you can always check which ones work, but each term in negative, so the number out fron must be negative

Answer 3

For Question one this is answer: an = -4 • 2n - 1

Answer 4

if \(n=1\) you should get \(-4\) and i think only
\[-4\times 2^{n-1}\] works

Answer 5

@misty1212 so is an = -4 • 2^(n - 1) correct?

Answer 6

yes

Answer 7

thank you both @misty1212 for the second question I know it isn't an = 3 • 4^(n - 1) but i hv no idea what it is

Answer 8

@freckles

Answer 9

you are supposed to get something that looks like \[a_n=a_0\times r^{n-1}\]

Answer 10

\[a_2=-12\\
a_5=768\]

Answer 11

is it A? @misty1212

Answer 12

divide and get \[\frac{a_5}{a_2}=\frac{768}{-12}=-64\]

Answer 13

idk i can't eyeball it, we have to do it

Answer 14

that means \[r^3=-64\] so \[r=-4\]

Answer 15

then go with C since it is the one that looks like \[a_0r^{n-1}\] in this case \(r=-4\) and \(a_0=3\) since \[3\times (-4)^{2-1}=3\times -4=-12\]

Answer 16

thanks @misty1212