1+4+7+…+(3n+1)=(n+1)(3n+2)/2

证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n lim(1/n^2+4/n^2+7/n^2+…+3n-1/n^2) 证明：1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+) (1/(n^2 n 1 ) 2/(n^2 n 2) 3/(n^2 n 3) ……n/(n^2 n n)) 当N越于无穷大 1 + (n + 1) + n*(n + 1) + n*n + (n + 1) + 1 = 2n^2 + 3n + 3 用数学归纳法证明：1×2×3+2×3×4+…+n×(n+1)×(n+2)＝n(n+1)(n+2)(n+3)4(n∈N 求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n), 化简：1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4) (n+1)(n+2)/1 +(n+2)(n+3)/1 +(n+3)(n+4)/1 证明(1+2/n)^n>5-2/n（n属于N+,n>=3) [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 化简(n+1)(n+2)(n+3)