$$\eqalign{
& x.x.x - 7x - 6 \cr
& = {x^3} - 7x - 6 \cr
& = {x^3} + 1 - 7x - 7 \cr
& = \left( {{x^3} + 1} \right) - 7\left( {x + 1} \right) \cr
& = \left( {x + 1} \right)\left( {{x^2} - x + 1} \right) - 7\left( {x + 1} \right) \cr
& = \left( {x + 1} \right)\left( {{x^2} - x + 1 - 7} \right) \cr
& = \left( {x + 1} \right)\left( {{x^2} - x - 6} \right) \cr
& = \left( {x + 1} \right)\left( {{x^2} + 2x - 3x - 6x} \right) \cr
& = \left( {x + 1} \right)\left[ {x\left( {x + 2} \right) - 3\left( {x + 2} \right)} \right] \cr
& = \left( {x + 1} \right)\left( {x + 2} \right)\left( {x - 3} \right) \cr} $$
