`@Kem`
`3x^2-22xy-4x+8y+7y^2+1`
Giả sử:`\(A=\left(3x+ay+b\right)\left(x+cy+d\right)\)`
`\(=3x^2+3cxy+3dx+axy+acy^2+ady+bx+bcy+bd\)`
`\(=3x^2+acy^2+\left(3c+a\right)xy+\left(3d+b\right)x+\left(ad+bc\right)y+bd\)`
Ta có:`\(\begin{cases}\begin{matrix}ac=-7\\3c+a=-22\\3d+b=-4\\ad+bc=8\end{matrix}\\bd=1\end{cases}\)\(\Rightarrow\begin{cases}a=-1\\b=-1\\c=-7\\d=-1\end{cases}\)`
Vậy `\(A=\left(3x-y-1\right)\left(x-7y-1\right)\)`
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`12x^2 + 5x - 12y² + 12y - 10xy - 3 `
`= (12x^2 - 18xy + 9x) - (4x - 6y + 3) + (8xy - 12y^2 + 6y) `
`= 3x(4x - 6y + 3) - (4x - 6y + 3) + 2y(4x - 6y + 3) `
`= (4x - 6y + 3)(3x + 2y - 1) `
