A(A+1)(A+2)(A+3)+1
= A(A+3) * (A+1)(A+2) + 1
= (A^2 + 3A) * (A^2 + 3A + 2) + 1
令B = A^2 + 3A，则：
(A^2 + 3A) * (A^2 + 3A + 2) + 1
= B * (B + 2) + 1
= B^2 + 2B + 1
= (B + 1)^2
= (A^2 + 3A + 1)^2
A(A+1)(A+2)(A+3)+1
= A(A+3) * (A+1)(A+2) + 1
= (A^2 + 3A) * (A^2 + 3A + 2) + 1
=(A^2 + 3A)^2+2(A^2 + 3A)+1
=(A^2 + 3A+1)^2
内容全部来源于网络收集，如有侵权，请联系网站删除！
QQ：24596024