(x²+4)²-(2x+3)²
=(x²+4+2x+3)(x²+4-2x-3)
=(x²+2x+7)(x²-2x+1)
=(x²+2x+7)(x-1)²
(99²+199)/(99²+99)
=(99²+2×99+1)/(99²+99)
=(99+1)²/[99×)99+1)]
=(99+1)*99
=99分之100
4a²b²-（2x+3）²
=(2ab+2x+3)(2ab-2x-3)4a²b²-（2x+3）²换成4a²b²-（a²+b²）²应该怎么算？=-[(a²+b²)²-(2ab)²]=-(a²+b²+2ab)(a²+b²-2ab)=-(a+b)²(a-b)²