令x=2005则根号内=a(a+1)(a+2)(a+3)+1=[a(a+3)][(a+1)(a+2)+1=(a²+3a)(a²+3a+2)+1=(a²+3a)²+2(a²+3a)+1=(a²+3a+1)²所以原式=a²+3a+1-a²=3a+1=6016