$x^{3}-2 x^{2}-x+2$

Rearranging the terms, we have

$x^{3}-2 x^{2}-x+2=x^{3}-x-2 x^{2}+2=x\left(x^{2}-1\right)-2\left(x^{2}-1\right)$

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

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

$=(x-1)(x+1)(x-2)$

$\left[\because a ^{2}- b ^{2}=( a + b )( a – b )\right]$

Thus,  $x^{3}-2 x^{2}-x+2=(x-1)(x+1)(x-2)$