Applicare la formula: $\frac{\frac{a}{b}}{\frac{c}{f}}$$=\frac{af}{bc}$, dove $a=3x^2$, $b=\left(x^2+1\right)^2$, $a/b/c/f=\frac{\frac{3x^2}{\left(x^2+1\right)^2}}{\frac{x}{x^2+1}}$, $c=x$, $a/b=\frac{3x^2}{\left(x^2+1\right)^2}$, $f=x^2+1$ e $c/f=\frac{x}{x^2+1}$

Applicare la formula: $\frac{a^n}{a}$$=a^{\left(n-1\right)}$, dove $a^n/a=\frac{3x^2\left(x^2+1\right)}{\left(x^2+1\right)^2x}$, $a^n=x^2$, $a=x$ e $n=2$

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