Question

ほんだし@公式

この式を言葉で説明して頂けませんか？

= x¹-2x²y² + y²-2x²-2y²+1
21 (1) 与式
={a+(b+c)}{a² − (b+c)a+(b²-bc+c²)}
= a{a²-(b+c)a+(b²-bc+c²)}
+(b+c){a²-(b+c)a+(b²-bc+c²)}
=a³-(b+c)a² + (b²-bc+c²) a
+(b+c)a²-(b + c)²a +(b+c)(b²-bc+c²)
=a³+ ((b²-bc+c)-(b²+2bc+c²)}a+(b³ + c³)
=a³-3bc•a+b³ + c³=a³ + b³ + c³-3abc
3