Answer
$$x ∈ (-1, 4)$$
Also see the image below.
Work Step by Step
$3x^2-3x<2x^2+4$
$3x^2-3x$ is represented as the Blue graph on the image above.
$2x^2+4$ is represented as the Red graph on the image above.
We have to find the region, where the Blue graph is below the Red one. That is the region between points $A$ and $B$
$x ∈ (-1, 4)$
