1. patchwork method (first find the common factor according to experience, and then solve it by short division)

=(λ? -4λ? )+(λ? -4λ)-(2λ-8)

=λ? (λ-4)+λ(λ-4)-2(λ-4)

=(λ? +λ-2)×(λ-4)

=(λ+2)×(λ- 1)×(λ-4)

2. Use cubic summation formula

Answer? +b？ =(a+b)x(a？ -ab+b？ )

Original formula = λ? +2? -3λ? -6λ

=(λ+2)×(λ? -2λ+4)-3λ? -6λ

=(λ+2)×(λ? -2λ+4-3λ)

=(λ+2)×(λ? -5λ+4) crossing

=(λ+2)×(λ-4)×(λ- 1)