\(4\left(x-2\right)\left(x-3\right)\left(x-4\right)\left(x-6\right)-3x^2\)
\(=4\left(x-2\right)\left(x-6\right)\left(x-3\right)\left(x-4\right)-3x^2\)
\(=4\left(x^2-8x+12\right)\left(x^2-7x+12\right)-3x^2\)
Đặt: \(x^2-8x+12=y\)
\(\Leftrightarrow4y\left(y-x\right)-3x^2\)
\(=4y^2-4yx-3x^2\)
\(=\left(2y+x\right)\left(2y-3x\right)\)
\(=\left(2x^2-15x+24\right)\left(2x^2-19x+24\right)\)