3n+1+20=3(n+1)+1-2
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
1 + (n + 1) + n*(n + 1) + n*n + (n + 1) + 1 = 2n^2 + 3n + 3
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
证明:1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+)
化简(n+1)(n+2)(n+3)
1\n(n+3)+1\(n+3)(n+6)+1\(n+6)(n+9)=1\2 n+18 n为正整数,求n的值
求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n),
若n²+3n=1,求n(n+1)(n+2)+1的值.
计算:n(n+1)(n+2)(n+3)+1
lim[(n+3)/(n+1))]^(n-2) 【n无穷大】
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)..