1) \(x^2+x-6\)
\(=x^2+3x-2x-6\)
\(=x\left(x-3\right)-2\left(x-3\right)\)
\(=\left(x-3\right)\left(x-2\right)\)
2) \(x^2-3x+2\)
\(=x^2+4x-x+2\)
\(=x\left(x+2\right)-\left(x+2\right)\)
\(=\left(x+2\right)\left(x-1\right)\)
3) \(x^2-4x+3\)
\(=x^2-3x-x+3\)
\(=x\left(x-3\right)-\left(x-3\right)\)
\(=\left(x-3\right)\left(x-1\right)\)