a²x²+16ax+64
=(ax)²+2·8·ax+8²
=(ax+8)²
（a²+4）²-16²
=(a²+4+16)(a²+4-16)
=(a²+20)(a²-(2√3)²)
=(a²+20)(a+2√3)(a-2√3)√怎么写？？”√“表示根号哦