Answer
Error: the value of the common ratio
The correct common ratio: $-\frac{1}{2}$ and not $-2$.
The next three terms are
$-\frac{1}{2},\frac{1}{4},-\frac{1}{8}$
Work Step by Step
The common ratio is shown as $-2$ which is not correct. The common ratio is $-\frac{1}{2}$.
The next three terms therefore are
$1\times\left(-\frac{1}{2}\right)=-\frac{1}{2}$
$-\frac{1}{2}\times\left(-\frac{1}{2}\right)=\frac{1}{4}$
$\frac{1}{4}\times\left(-\frac{1}{2}\right)=-\frac{1}{8}$
