本もとを正ただす

expression, godan verb (-su)

get to the bottom of something; trace back to the origin; investigate the root cause

Used when thoroughly examining the fundamental cause or origin of a matter, often in formal or investigative contexts.

See also: 糺す

• この問もん題だいは本もとを正たださないと解かい決けつできない。

  We can't solve this problem unless we get to the bottom of it.

• 記き者しゃは事じ件けんの本もとを正ただすために現げん地ちへ向むかった。

  The reporter went to the site to investigate the root of the incident.