Answer
$-(x-1)(x-4)$
Work Step by Step
Factoring $
-1
,$ the given expression, $
-x^2+5x-4
,$ is equivalent to
\begin{align*}
-(x^2-5x+4)
.\end{align*}
Using the factoring of trinomials in the form $x^2+bx+c,$ the expression above has $c=
4
$ and $b=
-5
.$
The two numbers with a product of $c$ and a sum of $b$ are $\left\{
-1,-4
\right\}.$ Using these two numbers, the factored form of the expression above is
\begin{align*}
-(x-1)(x-4)
.\end{align*}