Ta có: \(2y^3-6y^2+12y-8\)
\(=2\left(y^3-3y^2+6y-4\right)\)
\(=2\left(y^3-y^2-2y^2+2y+4y-4\right)\)
\(=2\left(y-1\right)\left(y^2-2y+4\right)\)
\(2y^3-6y^2+12y-8=2y^3-4y^2-2y^2+8y+4y-8\)
\(=\left(2y^3-4y^2+8y\right)-\left(2y^2-4y+8\right)\)
\(=\left(2y^2-4y+8\right)y-\left(2y^2-4y+8\right)\)
\(=\left(y-1\right)\left(2y^2-4y+8\right)\)
\(=2\left(y-1\right)\left(y^2-2y+4\right)\)