\(x^2-x-6\)\(=x^2-3x+2x-6\)\(=x\left(x-3\right)+2\left(x-3\right)\)\(=\left(x-3\right)\left(x+2\right)\)\(x^4-4\)\(=x^4+4+4x^2-4x^2\)\(=\left(x^2+2\right)^2-4x^2\)=\(\left(x^2+2-2x\right)\left(x^2-2+2x\right)\)Câu trả lời: \(x^2-x-6\)\(=x^2-3x+2x-6\)\(=x\left(x-3\right)+2\left(x-3\right)\)\(=\left(x-3\right)\left(x+2\right)\)\(x^4-4\)\(=x^4+4+4x^2-4x^2\)\(=\left(x^2+2\right)^2-4x^2\)=\(\left(x^2+2-2x\right)\left(x^2-2+2x\right)\)