Chọn câu sai.

Ta có

+) Đáp án A đúng vì:

 \(\begin{array}{l}16{x^3} - 54{y^3} = 2\left( {8{x^3} - 27{y^3}} \right)\\ = 2\left[ {{{\left( {2x} \right)}^3} - {{\left( {3y} \right)}^3}} \right]\\ = 2\left( {2x - 3y} \right)\left[ {{{\left( {2x} \right)}^2} + 2x.3y + {{\left( {3y} \right)}^2}} \right]\\ = 2\left( {2x - 3y} \right)\left( {4{x^2} + 6xy + 9{y^2}} \right).\end{array}\)  

+) Đáp án B đúng vì:

\(\begin{array}{l}{x^2} - 9 + \left( {2x + 7} \right)\left( {3 - x} \right)\\ = \left( {{x^2} - 9} \right) + \left( {2x + 7} \right)\left( {3 - x} \right)\\ = \left( {x - 3} \right)\left( {x + 3} \right) - \left( {2x + 7} \right)\left( {x - 3} \right)\\ = \left( {x - 3} \right)\left( {x + 3 - 2x - 7} \right)\\ = \left( {x - 3} \right)\left( { - x - 4} \right)\end{array}\)

+) Đáp án C đúng vì:

\(\begin{array}{l}\;{x^4} - 4{x^3} + 4{x^2} = {x^2}\left( {{x^2} - 4x + 4} \right)\\ = {x^2}\left( {{x^2} - 2.2.x + {2^2}} \right) = {x^2}{\left( {x - 2} \right)^2}.\end{array}\)

+) Đáp án D sai vì:

\(\begin{array}{l}\;4{x^3} - 4{x^2} - x + 1\\ = \left( {4{x^3} - 4{x^2}} \right) - \left( {x - 1} \right)\\ = 4{x^2}\left( {x - 1} \right) - \left( {x - 1} \right)\\ = \left( {4{x^2} - 1} \right)\left( {x - 1} \right)\\ = \left( {{{\left( {2x} \right)}^2} - 1} \right)\left( {x - 1} \right)\\ = \left( {2x - 1} \right)\left( {2x + 1} \right)\left( {x - 1} \right).\end{array}\)