恒こう等とう式しき

noun

identity (mathematics)

A mathematical equation that holds true for all values of its variables. Used in algebra and other branches of mathematics.

• この式しきは恒こう等とう式しきなので、xにどんな値ちを代だい入にゅうしても成なり立たつ。

  Since this expression is an identity, it holds true no matter what value you substitute for x.