\(=\left(x^2+2x+5\right)-x\left(x^2+2x+5\right)-6x\left(x^2+2x+5\right)+6x^2\)
\(=\left(x^2+2x+5\right)\left(x^2+2x+5-x\right)-6x\left(x^2+2x+5-x\right)\)
\(=\left(x^2+2x+5\right)\left(x^2+x+5\right)-6x\left(x^2+x+5\right)\)
\(=\left(x^2+x+5\right)\left(x^2+2x+5-6x\right)\)
\(=\left(x^2+x+5\right)\left(x^2-4x+5\right)\)