`(x^4-x^3-3x^2+x+2):(x^2-1)`
`=[(x^3−3x−2)(x−1)]:(x^2−1) `
`=[(x^2−x−2)(x+1)(x−1)]:(x^2-1)`
`=[(x−2)(x+1)(x+1)(x−1)]:(x^2−1)`
`=[(x−2)(x+1)^2(x−1)]:(x^2−1)`
`=[(x−2)(x+1)^2(x-1)]:[(x+1)(x−1)]`
`=[(x−2)(x+1)^2]:(x+1)`
`=(x−2)(x+1)`
`=x^2-x-2`