Question

Write an expression for the general or nth term, an, for the geometric sequence. 1, -4, 16, -64, . . .

Answer 1

HELP!

Answer 2

The general form for a geometric sequence is given by:
\[\Large\rm a_n=a_1 (r)^{n-1}\]So we just need to find a couple things:
a1 (The first term)
r (the common ratio between each term)

Answer 3

a1 is pretty straight forward, yes?
It appears that 1 is our first number in the sequence.
So we can eliminate option D.

Answer 4

We multiplied our first term by something.... in order to get to the second term.
If it's not clear what that "something" is, then divide the second term by the first term.
That will tell you your common ratio.\[\Large\rm r=\frac{a_2}{a_1}\]

\[\Large\rm r=\frac{-4}{1}\]

Answer 5

right..

Answer 6

i believe it is A

Answer 7

A is correct