2 sentences

1. 他的数学根基非常扎实。

   tā de shù​xué gēn​jī fēi​cháng zhā​shi.

   His foundation in mathematics is very solid.

   Source: Dong Chinese Dictionary

2. 古书云“本深则标茂”，以此强调根基的重要性。

   gǔ​shū yún“ běn shēn zé biāo mào”, yǐ cǐ qiáng​diào gēn​jī de zhòng​yào​xìng.

   Ancient texts state that 'when the roots are deep, the branches flourish,' emphasizing the importance of a solid foundation.

   Source: Dong Chinese Dictionary