Fill in ... in the following.

Recall the definition: x is rational if there exist integers m and n such that n > 0 and ...

Try proving (i) => (ii). Assume that x is rational. Then there exist m and n such that ... I need to show that x / 2 is rational. This means proving that there exist integers m' and n' such that x / 2 = ... Can I come up with such m' and n'?