Applicare la formula: $x+a=b$$\to x=b-a$, dove $a=2b$, $b=0$, $x+a=b=2a+2b=0$, $x=2a$ e $x+a=2a+2b$

Applicare la formula: $mx=ny$$\to \frac{m}{mcd\left(m,n\right)}x=\frac{n}{mcd\left(m,n\right)}y$, dove $x=a$, $y=b$, $mx=ny=2a=-2b$, $mx=2a$, $ny=-2b$, $m=2$ e $n=-2$

Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=2$, $b=2$ e $a/b=\frac{2}{2}$

Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=-2$, $b=2$ e $a/b=-\frac{2}{2}$