Tính \(\left( {x - 2} \right)\left( {x - 3} \right).4 - {x^2}\).

\(\begin{array}{l}\left( {x - 2} \right)\left( {x - 3} \right).4 - {x^2}\\ = ({x^2} - 3x - 2x + 6).4 - {x^2}\\ = 4{x^2} - 12x - 8x + 24 - {x^2}\\ = 3{x^2} - 20x + 24\end{array}\)