Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=\frac{42}{5}$, $b=1$ e $a/b=\frac{8.4}{1}$

Applicare la formula: $\frac{a}{b}c$$=\frac{ca}{b}$, dove $a=1$, $b=4$, $c=-2$, $a/b=\frac{1}{4}$ e $ca/b=-2\cdot \left(\frac{1}{4}\right)$

Applicare la formula: $ab$$=ab$, dove $ab=-2\cdot 1$, $a=-2$ e $b=1$

Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=-2$, $b=4$ e $a/b=-\frac{2}{4}$

Applicare la formula: $a+b$$=a+b$, dove $a=\frac{42}{5}$, $b=-\frac{1}{2}$ e $a+b=8.4-0.5$