ㄆㄢˊㄍㄣㄐㄧㄡˋㄉㄧˇpángēn‑jiùdǐ

盘根究底
pángēn‑jiūdǐㄆㄢˊ ㄍㄣ ㄐㄧㄡ ㄉㄧˇ
  1. 盤查根源追究底細 一定盤根究底不可輕忽」。

lit. to examine roots and inquire at the base (idiom)​; to get to the bottom of sth