计算1/6+1/12+1/20+...+1/n^2+3n+2

计算：n(n+1)(n+2)(n+3)+1 计算9^n*(1/27)^n+1*3^n+2 计算:(3a^n+2+6a^n+1-9^n)÷3a^n-1 计算：C(1,n)+2C(2,n)+3C(3,n) + … + nC(n,n) 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 n个自然数:1,2,3…,n,其平方和可用公式n(n+1)(2n+1)/6来计算,试计算11*11+12*12+ 用夹逼准则和重要极限两种方法计算极限lim(2^n+3^n+4^n+5^n+6^n)^(1/n)n趋近于... 计算级数 ∑n/2^(n-1) n阶行列式计算|1 2 3.n-1 n||2 1 3.n-1 n||2 3 1.n-1 n||.||2 3 4. 1 n 如果,n是大于2的整数,计算1/(n-1)(n-2)+1/(n-2)(n-3)+1/(n-3)(n-4)+……+1/(n 计算(x^(2n)+x^n+1)(x^(3n)-x^(2n)+1)