Phân tích đa thức \({x^7} - {x^2} - 1\) thành nhân tử ta được

\(\left( {x - 5} \right)\left( {x + 2} \right)\).

\(\left( {x - 5} \right)\left( {x - 2} \right)\).

\(\left( {x + 5} \right)\left( {x + 2} \right)\).

\(\left( {x - 5} \right)\left( {2 - x} \right)\).

\(\left( {m - 1} \right)\left( {n + 1} \right)\left( {{n^2} - n + 1} \right)\)

\({n^2}\left( {n + 1} \right)\left( {m - 1} \right)\)

\(\left( {m + 1} \right)\left( {{n^2} + 1} \right)\)

\(\left( {{n^3} + 1} \right)\left( {m - 1} \right)\)

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

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

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

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

\(2x + y + 1\)

\(2x - y + 1\)

\(2x - y\)         

\(2x + y\)

\({x^3} + {x^2} - 4x - 4 = \left( {x - 2} \right)\left( {x + 2} \right)\left( {x + 1} \right)\).

\({x^2} + 10x + 24 = \left( {x + 4} \right)\left( {x + 6} \right)\).              

Cả A, B đều sai

Cả A, B đều đúng.

\(16{x^3} - 54{y^3} = 2\left( {2x - 3y} \right)\left( {4{x^2} + 6xy + 9{y^2}} \right)\).

\({x^2} - 9 + \left( {2x + 7} \right)\left( {3 - x} \right) = \left( {x - 3} \right)\left( { - x - 4} \right)\).

\(\;{x^4} - 4{x^3} + 4{x^2} = {x^2}{\left( {x - 2} \right)^2}.\)    

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

\(\left( A \right)\) đúng, \(\left( B \right)\) sai.

\(\left( A \right)\) sai, \(\left( B \right)\) đúng.

\(\left( A \right)\), \(\left( B \right)\) đều sai

\(\left( A \right)\), \(\left( B \right)\) đều đúng.