Applicare la formula: $\frac{a}{b}\frac{c}{f}$$=\frac{ac}{bf}$, dove $a=x^2-1$, $b=x^2-x-2$, $c=x^2+x-2$, $a/b=\frac{x^2-1}{x^2-x-2}$, $f=x^2-4$, $c/f=\frac{x^2+x-2}{x^2-4}$ e $a/bc/f=\frac{x^2-1}{x^2-x-2}y\frac{x^2+x-2}{x^2-4}$

Applicare la formula: $a\frac{b}{c}$$=\frac{ba}{c}$, dove $a=y$, $b=\left(x^2-1\right)\left(x^2+x-2\right)$ e $c=\left(x^2-x-2\right)\left(x^2-4\right)$