LECTURE NOTES IN ANALYSIS (2011)
《LECTURE NOTES IN ANALYSIS (2011)》 · 第 50 页 · Section 2.1「Congruences」
For fixed integers $a$ and $m>0$, the set of all integers $x$ satisfying $xequiv apmod m$ is the arithmetic progression $\ldots,a-2m,a-m,a,a+m,a+2m,\ldots$. This set is called a residue class, or congruence class, modulo $m$.