(a-b-c)(b-a-c)(c-a-b)= (a-b-c) [a+(c-b) ] [ a-（c-b) ] =(a-b-c) [a²-(c-b) ²] =a³-（b+c）a²+（b+c）(c-b) ² = a³-（b+c）a²+（c²-b²）(c-b) = a³+b ³+c ³-（b+c）a²-c ²b-b ²c
