Question

Determine whether the following sequence is geometric. If so, find the common ratio. 1, -4, 16, -64, . . .

Answer 1

Given:

Geometric sequence is:

1,-4,16,-64

Sol:

For geometric sequence is:

`a_n=a_1r^(n-1)`
`\begin{gathered} a_1=1 \\ a_2=-4 \end{gathered}`
`\begin{gathered} a_n=a_1r^(n-1) \\ -4=1r^(2-1) \\ -4=r \end{gathered}`

Common ratio is -4.