\(\begin{array}{l}j)\,4x\left( {x - 2y} \right) + 12y\left( {2y - x} \right)\\ = \left( {x - 2y} \right)\left( {4x - 12y} \right)\\k)\,{x^2} - 6x + 5\\ = {x^2} - x - 5x + 5\\ = x\left( {x - 1} \right) - 5\left( {x - 1} \right)\\ = \left( {x - 1} \right)\left( {x - 5} \right)\end{array}\)
\(\begin{array}{l}{x^4} + 64\\ = {\left( {{x^2}} \right)^2} + {8^2} + 2{x^2}.8 - 2.{x^2}.8\\ = {\left( {{x^2} + 8} \right)^2} - {\left( {4x} \right)^2}\\ = \left( {{x^2} - 4x + 8} \right)\left( {{x^2} + 4x + 8} \right)\end{array}\)
\(\begin{array}{l}n)\,4{x^4} + 81\\ = {\left( {2{x^2}} \right)^2} + {9^2} + 2.2{x^2}.9 - 2.2{x^2}.9\\ = {\left( {2{x^2} - 9} \right)^2} - 36{x^2}\\ = {\left( {2{x^2} - 9} \right)^2} - {\left( {6x} \right)^2}\\ = \left( {2{x^2} - 6x - 9} \right)\left( {2{x^2} + 6x - 9} \right)\end{array}\)
Các ý còn lại em tự làm tiếp nhé,
