Answer
Yes; $y=-1/2x$.
Work Step by Step
If y varies directly with x, then every point on the table should have the same value for y/x. If y/x has the same value at every point, then it will be direct variation, and y/x will be the constant of variation. Thus, we obtain:
$1/-2=-1/2 \\\\ -1/2=-1/2 \\\\ -2/4=-1/2$
It is direct variation, where $k=-1/2$. Thus, we substitute k to get the equation: $y=-1/2x$.
