Answer
$$x∈[-2, 0.25]$$
Also see the image below.
Work Step by Step
$0.5x^2+0.875x\leq 0.25$
For a better visualization, we will align the inequality to form two separate equations.
$0.5x^2\leq -0.875x+0.25$
$0.5x^2$ is represented as the Blue graph on the image above.
$-0.875x+0.25$ is the Red graph on the image above.
As we can see, they intersect at points $A$ and $B$. Solution lays between them, in the region $[-2, 0.25]$
