= a^3.(b^2-c^2)+b^3.(c^2-b^2+b^2-a^2)+c^3.(a^2-b^2)
=a^3.(b^2-c^2) - b^3.(b^2-c^2 ) -b^3.(a^2-b^2)+c^3(a^2-b^2)
= (b^2 -c^2).(a^3-b^3) -(a^2-b^2).(b^3-c^3)
= (b-c)(b+c)(a-b)(a^2+ab+b^2)-(a-b)(a+b)(b-c)(b^2+bc +c^2)
=(b-c)(a-b).(b.a^2 +ab^2 +b^3 +ca^2 +abc +cb^2 - ab^2- abc - ac^2 - b^3-b^2 .c -bc^2)
=(b-c)(a-b)(a^2.b +ca^2 -ac^2-bc^2)
=(b-c)(a-b)(a-c)(ab+bc+ac)