Answer
$a_{1}=(-\frac{1}{2})^{1-1}=(-\frac{1}{2})^{0}=1$
$a_{2}=(-\frac{1}{2})^{2-1}=(-\frac{1}{2})^{1}=-\frac{1}{2}$
$a_{3}=(-\frac{1}{2})^{3-1}=(-\frac{1}{2})^{2}=\frac{1}{4}$
$a_{4}=(-\frac{1}{2})^{4-1}=(-\frac{1}{2})^{3}=-\frac{1}{8}$
$a_{10}=(-\frac{1}{2})^{10-1}=(-\frac{1}{2})^{9}=-\frac{1}{512}$
$a_{15}=(-\frac{1}{2})^{15-1}=(-\frac{1}{2})^{14}=\frac{1}{16384}$
Work Step by Step
If we want to find a term, we have to substitute $n$ by its index:
$a_{1}=(-\frac{1}{2})^{1-1}=(-\frac{1}{2})^{0}=1$
$a_{2}=(-\frac{1}{2})^{2-1}=(-\frac{1}{2})^{1}=-\frac{1}{2}$
$a_{3}=(-\frac{1}{2})^{3-1}=(-\frac{1}{2})^{2}=\frac{1}{4}$
$a_{4}=(-\frac{1}{2})^{4-1}=(-\frac{1}{2})^{3}=-\frac{1}{8}$
$a_{10}=(-\frac{1}{2})^{10-1}=(-\frac{1}{2})^{9}=-\frac{1}{512}$
$a_{15}=(-\frac{1}{2})^{15-1}=(-\frac{1}{2})^{14}=\frac{1}{16384}$
