$a)w\left(x\right)=x^3-x^2-x+1=x^2\left(x-1\right)-\left(x-1\right)=\left(x-1\right)\left(x^2-1\right)=$

$=\left(x-1\right)\left(x-1\right)\left(x+1\right)={\left(x-1\right)}^2\left(x+1\right)$

$b)w\left(x\right)=x^5+x^4-x-1=x^4\left(x+1\right)-\left(x+1\right)=\left(x+1\right)\left(x^4-1\right)=$

$=\left(x+1\right)\left(x^2-1\right)\stackrel{\Delta =0-4<0}{\left(x^2+1\right)}=\left(x+1\right)\left(x-1\right)\left(x+1\right)\left(x^2+1\right)=$