Question

Find the multiplicative inverse of $3$ and $-7$.

Answer 1

The multiplicative identity for rational numbers with out $0$ is $1$. [ Since the rational numbers forms a group with respect to multiplication of rational numbers]

Now the multiplicative inverse of $3$ and $-7$ are $\frac{1}{3}$ and $-\frac{1}{7}$ as $3.\frac{1}{3}=\frac{1}{3}.3=1$ and $(-7).-\frac{1}{7}=-\frac{1}{7}.(-7)=1$.