Chọn  câu đúng.

\(\left( {5x - 2y} \right)\left( {x + 4y} \right)\)           

\(\left( {5x + 4} \right)\left( {x - 2y} \right)\)

\(\left( {x + 2y} \right)\left( {5x - 4} \right)\)

\(\left( {5x - 4} \right)\left( {x - 2y} \right)\)

\(\left( {{a^2} + b} \right)\left( {5x - 2y} \right)\).

\(\left( {{a^2} - b} \right)\left( {2x - 5y} \right)\).

\(\left( {{a^2} + b} \right)\left( {2x + 5y} \right)\).

\(\left( {{a^2} + b} \right)\left( {2x - 5y} \right)\).

\(\left( {x + y + 2xy} \right)\) 

\(\left( {x - y + 2xy} \right)\)  

\(\left( {x - y + xy} \right)\)

\(\left( {x - y + 3xy} \right)\)

\(ax - bx + ab - {x^2} = \left( {x + b} \right)\left( {a - x} \right)\).

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

\(ax + ay - 3x - 3y = \left( {a - 3} \right)\left( {x + y} \right)\).         

\(xy + 1 - x - y = \left( {x - 1} \right)\left( {y - 1} \right)\)

\(m = 5;\,n =  - 1\).

\(m =  - 5;\,n =  - 1\).

\(m = 5;\,n = 1\).

\(m =  - 5;\,n = 1\).

\(m < 0\).

\(1 < m < 3\).

\(2 < m < 4\).

\(m > 4\).