Question

Find a formula for the nth term of the sequence whose first few terms are shown.
-1/8, -1/2, -2, -8, -32

Answer 1

\[
a_1= -\frac 18\\
a_{n+1} = 4 a_n,\quad n>1
\]

Answer 2

\[
a_n = -\frac 1 8 4^{n-1}
\]

Answer 3

thank you very much