Thực hiện phép tính: a) $\frac{{24{y^5}}}{{7{x^2}}}.\left( { - \frac{{12{y^3}}}} \right)$ ; b) $- \frac{{36{y^3}}}{{15{x^4}}}.\left( { - \frac{{45{x^2}}}{{9{y^3}}}} \right)$ ; c) $\frac{{{x^2} - {y^2}}}{{{x^2}}}.\frac{{{x^4}}}{{{{\left( {x + y} \right)}^2}}}$ ; d) $\frac{{{x^2} - 1}}.\frac}$ .

Thực hiện phép tính:

a) $\frac{{24{y^5}}}{{7{x^2}}}.\left( { - \frac{{12{y^3}}}} \right)$ ;

b) $- \frac{{36{y^3}}}{{15{x^4}}}.\left( { - \frac{{45{x^2}}}{{9{y^3}}}} \right)$ ;

c) $\frac{{{x^2} - {y^2}}}{{{x^2}}}.\frac{{{x^4}}}{{{{\left( {x + y} \right)}^2}}}$ ;

d) $\frac{{{x^2} - 1}}.\frac}$ .