It is exactly the same thing as finding roots.
Use synthetic division. I'll do plus and minus 1 for you:
1 | 1 4 1 -6
1 5 6
------------------
1 5 6 0
The remainder is zero, so
is a factor, so 1 is a root.
-1 | 1 4 1 -6
-1 -3 2
------------------
1 3 -2 4
The remainder is not zero, so
is not a factor, so -1 is not a root.
Note that in the division that proved
is a factor, the quotient is
, a factorable quadratic polynomial for which you should be able to determine the zeros.
John

My calculator said it, I believe it, that settles it