Answer
$y=-500x$
(see graph below)
Work Step by Step
Since $y$ varies directly as $x,$ then it follows the model $y=kx.$ Solving for $k$ by substituting the given point, $(
-0.1,50
),$ results to
\begin{array}{l}\require{cancel}
y=kx
\\
50=k(-0.1)
\\
\dfrac{50}{-0.1}=k
\\
k=-500
.\end{array}
Hence, the direct variation equation is $
y=-500x
.$
Using a table of values, the graph of $
y=-500x
$ is shown above.