\(x^2-6x+8\)
\(C1\) \(=x^2-4x-2x+8\)
\(=\left(x^2-4x\right)-\left(2x-8\right)\)
\(=x\left(x-4\right)-2\left(x-4\right)\)
\(=\left(x-2\right)\left(x-4\right)\)
\(C2\): \(x^2-6x+8\)
\(=x^2-6x+9-1\)
\(=\left(x^2-6x+9\right)-1\)
\(=\left(x-3\right)^2-1\)
\(=\left(x-3-1\right)\left(x-3+1\right)\)
\(=\left(x-4\right)\left(x-2\right)\)
\(C3\) \(x^2-6x+8\)
\(=x^2-2x-4x+8\)
\(=\left(x^2-2x\right)-\left(4x-8\right)\)
\(=x\left(x-2\right)-4\left(x-2\right)\)
\(=\left(x-2\right)\left(x-4\right)\)