-3a^n(a^n-1+2a^n-2+3a^n-3)+a^n-2(a^n-1-a^n+4a^n+1)超有挑战的因式分解!哪为天才能帮我?我以做出,但感觉答案不对．请求高人赐教!

a^n+2+a^n+1-3a^n因式分解 数列a(n)=n (n+1)(n+2)(n+3),求S(n) (3a^n+1+6a^n+2-9a^n)/3a^n-1 (6a^n+2 +3a^n+1 -9a^n)/3a^n-1 -a^n-(-5a^n-1)-2(a^n-1-3a^n) 计算:(3a^n+2+6a^n+1-9^n)÷3a^n-1 a^(n+1)b^n-4a^(n+2)+3ab^n-12a^2因式分解 如果n是正整数,[(8a^n+3)-(6a^n+2)-(5a^n+1)]/(-a)^n 1/3a^2n -(-7a^n)+(-1)^2n+1 a^n -(2/5a^2n)-5a^n(n为正整数） 计算 (3A^N+2*B-2A^N*B^N-1+3B^N)*5A^N*B^N+3(N为正整数,n＞1) (a^n+2)-(2a^n)+(3a^n-1) 因式分解a^（n+2)-2a^n+3a^（n-1) 分式 计算：a^(2n+1)-6a^(2n)+9a^(2n-1) / a^(n+1)-4a^n+3a^(n-1) 设a,n∈N*证明a^2n-(-a)^n≥(a+1)×a^n 计算:(a(1)+a(2)+.+a(n-1))(a(2)+a(3)+.+a(n))-(a(2)+a(3)+.+a(n-1))(a(1)+a(2)+.a(n)) 因式分解 a^4n+a^3n+a^2n+a^n 因式分解3a^n(1-a)-2(a^n-2a^n+1) n(n+1)+(n+1)(n+2)+(n+2)(n+3).(n+2a)(n+2a+1)用一个代数式表示谢谢schumiandmassa 与guoshiqiangaxv的回答， n边形所有对角线的条数是A n(n-1)/2 B n(n-2)/2 C n(n-3)/2 D n(n-4)/2