原式=a^4-2(b^2+c^2)a^2+b^4-2b^2c^2+c^4
=a^4-2(b^2+c^2)a^2+(b^2-c^2)^2
=a^4-2(b^2+c^2)a^2+(b+c)^2(b-c)^2
=[a^2-(b+c)^2][a^2-(b-c)^2]
=(a-b-c)(a+b+c)(a+b-c)(a-b+c)
原式=a^4-2(b^2+c^2)a^2+b^4-2b^2c^2+c^4
=a^4-2(b^2+c^2)a^2+(b^2-c^2)^2
=a^4-2(b^2+c^2)a^2+(b+c)^2(b-c)^2
=[a^2-(b+c)^2][a^2-(b-c)^2]
=(a-b-c)(a+b+c)(a+b-c)(a-b+c)