Question

Find an equation for the nth term of the sequence. -4, -16, -64, -256, ...

Answer 1

any ideas on what the "common ratio" or multiplier is?

what value you'd need to multiply the value to get the next value that is

Answer 2

hint: geometric

Answer 3

\(\large \bf a_{\color{red}{ n}}=a_1\cdot r^{{\color{red}{ n}}-1}\qquad
\begin{array}{llll}
a_1=\textit{1st term of sequence}\\
r=\textit{common ratio or multiplier}
\end{array}\)

Answer 4

Wait, so which of the options would it be?

a. an = 4 • -4n
b. an = 4 • -4n + 1
c. an = -4 • 4n
d. an = -4 • 4n - 1

Answer 5

@jdoe0001

Answer 6

well.. what did you get for the multiplier?

Answer 7

-4

Answer 8

@jdoe0001

Answer 9

so... -4 * -4 = -16 ?

because from -4 to -16.... if we use -4.... it should be the next term, which is -16

Answer 10

Whoops. So it's +4 so the answer is d. an = -4 • 4n - 1 right? @jdoe0001

Answer 11

r = +4. yeap... thus \(\large \bf a_{\color{red}{ n}}=a_1\cdot r^{{\color{red}{ n}}-1}\implies a_{\color{red}{ n}}=-4\cdot 4^{{\color{red}{ n}}-1}\)

Answer 12

Thanks!

Answer 13

yw