 The rational numbers can be expressed in the form \(j_1/j_2\), where \(j_1\) and \(j_2\) are integers, \(j_2\neq 0\). They form the most elementary number system that includes the integers and that is closed under division, except by 0. If \(q_1\) and \(q_2\) are rational numbers, \(q_1/q_2\) is also a rational number if \(q_2\neq 0\).