(a+b+c)³-a³-b³-c³=a³+b³+c³+3a²b+3ab²+3b²c+3bc²+3a²c+3ac²+6abc-a³-b³-c³=3a²b+3ab²+3b²c+3bc²+3a²c+3ac²+6abc=3(a²b+ab²+b²c+bc²+a²c+ac²+2abc)=3[ab(a+b)+bc(b+c)+ac(a+c)+2abc]
