Tính:

\(\frac{{{x^2} - 6x + 9}}{{{x^2} - 3x + 9}}.\frac{{{x^3} + 27}}{{3x - 9}}\);

\(\frac{{{x^2} - 6x + 9}}{{{x^2} - 3x + 9}}.\frac{{{x^3} + 27}}{{3x - 9}} = \frac{{{{\left( {x - 3} \right)}^2}}}{{{x^2} - 3x + 9}}.\frac{{\left( {x + 3} \right)\left( {{x^2} - 3x + 9} \right)}}{{3\left( {x - 3} \right)}}\)

\( = \frac{{{{\left( {x - 3} \right)}^2}\left( {x + 3} \right)\left( {{x^2} - 3x + 9} \right)}}{{3\left( {x - 3} \right)\left( {{x^2} - 3x + 9} \right)}} = \frac{{\left( {x - 3} \right)\left( {x + 3} \right)}}{3} = \frac{{{x^2} - 9}}{3}\).