恒等式
identity
因数分解
: factorization
$ (a + b)^2 = a^2 + 2ab + b^2
$ (a - b)^2 = a^2 - 2ab + b^2
二項係数
$ (a + b)(a - b) = a^2 - b^2
https://x.com/enlarge35781514/status/1997228192890007997
https://x.com/nabla_del/status/1872860917416988829
https://x.com/atsushifujioka/status/1873236331838751064
分散に関する恒等式