\(x^2-6x+5=x^2-2.3x+5=\left(x^2-2.3x+9\right)-9+5=\left(x-3\right)^2-4=\left(x-3\right)^2-2^2=\left(x-3-2\right)\left(x-3+2\right)=\left(x-5\right)\left(x-1\right)\)
.\(x^2-6x+5\)=\(x^2-2\times3x+5\)
Ta có: \(x^2-6x+5=x^2-x-5x+5\)
\(=\left(x^2-x\right)-\left(5x-5\right)\)
\(=x\left(x-1\right)-5\left(x-1\right)\)
\(=\left(x-1\right)\left(x-5\right)\)