identity
この問題はｋについての恒等式なので、まず与式を、ｋについて、解(とく)きます。
This problem is an equality of k so we first solve the assigned equation for k.
constancy, always
コウ / つね
etc., and so forth, class (first), quality, equal, similar
トウ / ひと.しい
style, ceremony, rite, function, method, system, form, expression
シキ / —