Question

Find an explicit rule for the nth term of the sequence.

-4, -8, -16, -32, ...

Answer 1

The general formula for the nth term of a geometric sequence is
\[n ^{th}\ term=ar ^{n-1}\]
where a is the first term and r is the common ratio.
The common ratio for the given sequence is found from:
\[r=\frac{-8}{-4}=you\ can\ calculate\]
Now just substitute the values of a and r into the general formula to get the explicit rule. Can you do that?

Answer 2

So this is my answer: an = -4 • 2n - 1

Answer 3

\[n ^{th}\ term=-4\times2^{n-1}\]