Question

Please help! I'll fan and medal
Find an equation for the nth term of the sequence.

-3, -12, -48, -192, ...

an = 4 • -3n + 1
an = -3 • 4n - 1
an = -3 • 4n
an = 4 • -3n

Answer 1

@freckles

Answer 2

@mathmate @yanasidlinskiy

Answer 3

Please help

Answer 4

.=multiplication?

Answer 5

ask yourself these questions:
what pattern do you notice?
is this a geometric or arithmetic sequence?
is there a common ratio or a common difference?
what can i do to get from a previous term to the term after?

Answer 6

Can you help me solve it?

Answer 7

I think you have not written your choices correctly

Answer 8

That's how they were

Answer 9

so there were no exponents in the choices?

Answer 10

Yes all of the "n" on the end of each choice is an exponent

Answer 11

ok well if you didn't know how to answer any of the questions i presented above
... then try this:
plug in 1 into all of your choices and see which one spots out the first term in your sequence (the -3)

Answer 12

How? I'm not good at these

Answer 13

how to replace n with 1 and evaluate?

Answer 14

wherever there is an n, you put 1

Answer 15

then see if you get the result a1=-3 from it

Answer 16

for example:
you should see two n's here
\[a_n=-4 \cdot 3^{n+1}\]

Answer 17

replace the n's with 1

Answer 18

Ohhhh okay

Answer 19

I got -3 as the first number am I right?

Answer 20

So it would either be B or C right?

Answer 21

which of those two choices given you -3 when you replace n with 1

Answer 22

B

Answer 23

sounds good
you can remember it like this
you have a common ratio
that means you can always do term divided by previous term and get the same number
that is you can do (term)/(previous term)=same number

so you can always just plug your numbers into
\[a_n=\text{ first term} \cdot (\text{common ratio number} )^{n-1}\]

Answer 24

Wow thank you so much so to clarify, I am correct with choice B?

Answer 25

that nth term right there only works for geometric sequences

Answer 26

"sounds good"<-----

Answer 27

well that is if you meant choice B to be a_n=-3 \cdot 4^{n-1}

Answer 28

Can you help with just one more? I can open a new question

Answer 29

\[a_n=-3 \cdot 4^{n-1}\]

Answer 30

Yes thank you so much