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