a)3x^2-22xy-4x+8y+7y^2+1 = (y - 3x + 1) (7y - x + 1)

\(A=3x^2-22xy-4x+8y+7y^2+1\)

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 \(A=\left(3x-y-1\right)\left(x-7y-1\right)\)

Chúc bạn học tốt ^^

Bài làm 

3x2 – 8x + 4 = (4x2 – 8x + 4) - x2 = (2x – 2)2 – x2 = (2x – 2 + x)(2x – 2 – x) 
= (x – 2)(3x – 2)

3x^2-22xy-4x+8y+7y^2+1 = (y - 3x + 1) (7y - x + 1)

3x^2−22xy−4x+8y+7y^2+1

=3x^2−21xy−3x−xy+7y^2+y−x+7y+1

=3x(x−7y−1)−y(x−7y−1)−(x−7y−1)

=(3x−y−1)(x−7y−1)

\(3x^2-22xy-4x+8y+7y^2+1\)

\(=3x^2-21xy=3x-xy+7y^2+y-x+7y+1\)

\(=3x.\left(x-7y-1\right)-y.\left(x-7y-1\right)-\left(x-7y-1\right)\)

\(=\left(3x-y-1\right)\left(x-7y-1\right)\)

~ Rất vui vì giúp đc bn ~