1 sentence

1. 老师在课堂上讲解了如何通过配方来解一元二次方程。

   lǎo​shī zài kè​táng shàng jiǎng​jiě le rú​hé tōng​guò pèi​fāng lái jiě yī​yuán'èr​cì fāng​chéng.

   The teacher explained in class how to solve quadratic equations by completing the square.

   Source: Dong Chinese Dictionary