解:ab+bc+ac

=(a+b+c)2－(a2＋b2＋c2)/2

=－1/2

a2b+ab2+b2c+bc2＋a2c＋ac2

=(a＋b＋c)3－(a3＋b3＋c3)

=-2/3－2abc

a2b+ab2+abc＋b2c＋bc2＋abc＋a2c＋ac2＋abc

=ab(a＋b＋c)＋bc(a＋b＋c)＋ac(a＋b＋c)

=(a＋b＋c)(ab＋bc＋ac)=－1/2

=－2/3－2abc+3abc,abc=1/6

a2b2＋b2c2＋a2c2

=(ab＋bc＋ac)2-2abc(a＋b＋c)

=－1/12

a^4+b^4+c^4

=(a2＋b2＋c2)2－2(a2b2＋b2c2＋a2c2)

=25/6