The math way to do this is to try all factors of 40/1: +/- (1,2,4,5,8,10,20,40) in order to find the only possible rational roots .( -1, -2, 2, 5 (2 is double))
You use synthetic division or regular to lower the order of the equation (which will lower the number of possible roots.
Faster is to use desmos.com and plug in y= P(x) and the zeros are obvious and you can click on the points on the x axis.

JACQUES D.
03/31/22
Hilda R.
I got this answer, but the program marks it as incorrect. I entered as 1,-1,2,-2 etc.03/31/22