I would consider the graph
y=(x+3)(2x-1)(2-x)
The roots are -3, 1/2, and 2
It is of the form
$$\\y=-ax^3+bx^2+cx+d\\\\
$Where a,b,c and d are real numbers and a is positive.$$$
**** I instantly know the shape of this graph. ****
Refer to this post that I did in the past to understand what I mean.
It will help you enormously if you understand this older post !!!
http://web2.0calc.com/questions/how-do-you-find-a-power-function-that-is-graphed
Here is the graph. I have hidden the y axis because it is not relevant.
you do not need a graphing calc to get this basic shape. It is easy to draw freehand.
The answer is all the x values where the graph is ABOVE the x axis. It is that easy!
You do not need to test any points!
Solutions $$(-\infty,-3)\;\;and\;\;(0.5,2)$$
If you have any questions please ask.
If you fully understand this you will be a step in front of many others :)