令a=2007
原式=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
=(2007²+3×2007+1)²
令a=2007
原式=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
=(2007²+3×2007+1)²