Answer
$\dfrac{-5}{16}$
Work Step by Step
Since, we have
$\sum_{i=1}^{4}(\dfrac{-1}{2})^i=(\dfrac{-1}{2})^1+(\dfrac{-1}{2})^2+(\dfrac{-1}{2})^3+(\dfrac{-1}{2})^4$
or, $=\dfrac{-1}{2}+\dfrac{1}{4}-\dfrac{1}{8}+\dfrac{1}{16}$
Hence, we get
$=\dfrac{-5}{16}$
