Let a and $b$ be integers where $a0$ and $b0.$ Prove that $\frac{a+b}{ab}$ is also a rational number.

Question: Step $1$

We use the definition of rational numbers for this proof. To use this definition, we must show that

and

are integers,

and

$0$

$x$ is rational if there exist integers $m$ and $n,$ where $x=\frac{m}{n}$ and $n0.$