Try doing synthetic division. So we have the polynomial Lets try some easy numbers, like to see if they satisfy the polynomial. By plugging in these numbers we can see that is a factor meaning that satisfies the polynomial. Now we can do synthetic division: (Make sure to put a 0 for all variables that are missing)

-1| 2 0 -5 -3

0 -2 2 3

2 -2 -3 0

So now we can see that are factors. Simply do the quadratic equation from here. (Sorry if some of the steps were unclear, I am not that great at explaining)