\(x^6-x^4-9x^3+9x^2\)
\(=x^6-x^5+x^5-x^4-9x^2\left(x-1\right)\)
\(=x^5\left(x-1\right)+x^4\left(x-1\right)-9x^2\left(x-1\right)\)
\(=\left(x-1\right)\left(x^5+x^4-9x^2\right)\)
\(x^6-x^4-9x^3+9x^2\)
\(=x^4.\left(x^2-1\right)-9x^2\left(x-1\right)\)
\(=x^4.\left(x-1\right)\left(x+1\right)-9x^2\left(x-1\right)\)
\(=\left(x-1\right)\left[x^4.\left(x+1\right)-9x^2\right]\)
\(=\left(x^5+x^4\right)\left(x-1\right)-\left(3x\right)^2\left(x-1\right)\)
\(=\left(x-1\right)\left(x^5+x^4-9x^2\right)\)
\(=\left(x-1\right)\left[x^5+x^2\left(x^2-3^2\right)\right]\)
\(=\left(x-1\right)x^2\left[x^3+\left(x+3\right)\left(x-3\right)\right]\)