Find the roots of x3-x2-10x-8=0

Answer 1

The coefficients are:
1 -1 -10 -8
which do not add up to zero. So (x-1) is not a factor.
If we change the sign of the odd powers, we get:
-1 -1 10 -8
which adds up to zero. So (x+1) is a factor.

Divide x3-x2-10x-8 by (x+1) to get
x²-2x-8 and factorize to find the other zeroes.