Answer
$-1-i$
Work Step by Step
Using $i^2=-1$ and the laws of exponents, the given expression, $
i^3-i^4
,$ is equivalent to
\begin{array}{l}\require{cancel}
i^2\cdot i-(i^2)^2
\\\\=
(-1)\cdot i-(-1)^2
\\\\=
-i-1
\\\\=
-1-i
.\end{array}