（a²+3a）²+2（a²+3a）+1
=(a²+3a)²+(a²+3a)+(a²+3a)+1
=(a²+3a)(a²+3a+1)+(a²+3a+1)
=(a²+3a+1)(a²+3a+1)
=(a²+3a+1)²
把（a²+3a）²+2（a²+3a）+1化简成（a²+3a+1）²的详
（a²+3a）²+2（a²+3a）+1
=(a²+3a)²+(a²+3a)+(a²+3a)+1
=(a²+3a)(a²+3a+1)+(a²+3a+1)
=(a²+3a+1)(a²+3a+1)
=(a²+3a+1)²