\(\begin{array}{l}
a)\,\dfrac{{14x{y^5}\left( {2x - 3y} \right)}}{{21{x^2}y{{\left( {2x - 3y} \right)}^2}}} = \dfrac{{7xy.2{y^4}.\left( {2x - 3y} \right)}}{{7xy.3x{{\left( {2x - 3y} \right)}^2}}} = \dfrac{{2{y^4}}}{{3x\left( {2x - 3y} \right)}}\\
b)\,\dfrac{{20{x^2} - 45}}{{{{\left( {2x + 3} \right)}^2}}} = \dfrac{{5\left( {4{x^2} - 9} \right)}}{{{{\left( {2x + 3} \right)}^2}}} = \dfrac{{5\left( {2x - 3} \right)\left( {2x + 3} \right)}}{{{{\left( {2x + 3} \right)}^2}}} = \dfrac{{5\left( {2x - 3} \right)}}{{2x + 3}}\\
c)\,\dfrac{{32x - 8{x^2} + 2{x^3}}}{{{x^3} + 64}} = \dfrac{{2x\left( {{x^2} - 4x + 16} \right)}}{{\left( {x + 4} \right)\left( {{x^2} - 4x + 16} \right)}} = \dfrac{{2x}}{{x + 4}}
\end{array}\)
