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

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