LECTURE NOTES IN ANALYSIS (2011)
《LECTURE NOTES IN ANALYSIS (2011)》 · 第 87 页 · Section 2.6「Prime Power Moduli」，Theorem 2.23
Hensel's lemma. Suppose that $f(x)$ is a polynomial with integral coefficients. If $f(a)=0\pmod {p^j}$ and $f'(a)\ne 0\pmod p$, then there is a unique $t\pmod p$ such that $f(a+tp^j)=0\pmod {p^{j+1}}$.