1.（n+3)(n-3)-(n+2)(n-2) 2.(-1+a)(-1-a)(1+b) 重要的是过程

证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 化简n分之n-1+n分之n-2+n分之n-3+.+n分之1 化简n分之n-1+n分之n-2+n分之n-3+.+n分之1 -2n+n^2+n^3还能化简吗? -n^3+8n^2-16n 化简(n+1)(n+2)(n+3) 当n为正偶数,求证n/(n-1)+n(n-2)/(n-1)(n-3)+...+n(n-2).2/(n-1)(n-3)...1=n 3(n-1)(n+3)-2(n-5)(n-2) lim(n+3)(4-n)/(n-1)(3-2n) lim(n^3+n)/(n^4-3n^2+1) lim2^n +3^n/2^n+1+3^n+1 2^n*3^n*5^n+2/30^n n(n+1)(n+2)(n+3)+1 因式分解 lim[(n+3)/(n+1))]^(n-2) 【n无穷大】 lim(2^n+3^n)^1 (n趋向无穷) n(n+1)(n+2)(n+3)+1等于多少