4b²c²-（b²+c²-a²）²
=[2bc+(b²+c²-a²)][2bc-(b²+c²-a²)]
=(2bc+b²+c²-a²)(2bc-b²-c²+a²)
=[(b+c)²-a²][a²-(b-c)²]
=(b+c+a)(b+c-a)(a+b-c)(a-b+c)
4b²c²-（b²+c²-a²）²
=[2bc+(b²+c²-a²)][2bc-(b²+c²-a²)]
=(2bc+b²+c²-a²)(2bc-b²-c²+a²)
=[(b+c)²-a²][a²-(b-c)²]
=(b+c+a)(b+c-a)(a+b-c)(a-b+c)