(a+b+c)^3=a^3+b^3+c^3+3ab^2+3ba^2+3ac^2+3ca^2+3bc^2+3cb^2+6abc=a^3+b^3+c^3+(3ab^2+3ba^2+3abc)+(3ac^2+3ca^2+3abc)+(3bc^2+3cb^2+3abc)-3abc=a^3+b^3+c^3+3ab(a+b+c)+3ac(a+b+c)+3bc(a+b+c)-3abc由于a+b+c=0=>0...
