Question

X to the fourth power minus x to the third power plus 2x to the second power minus 4x minus
8=0

Answer 1

regroup:
(x^4+2x^2-8)-(x^3+4x)=0
Factor: (x^2-2)(x^2+4)-x(x^2+4)=0
both terms have (x^2+4), so (x^2+4)(X^2-x-2)=0
factor again: (x^2+4)(x+1)(x-2)=0
x=1, x=2, x=2i, or x=-2i