1/4+1/(4*7)+1/(7*10)+1/(10*13)+...+1/(3n-2)*(3n+1)

lim(1/n^2+4/n^2+7/n^2+…+3n-1/n^2) 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^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 计算1/(m-n)-1/(m+n)-2n/(m^2+n^2)-4n^3/(m^4+n^4)-8n^7/(m^8+n^8) 已知888个连续正整数之和:n+(n+1)+(n+2)+(n+3)+(n+4)+(n+5)+(n+6)+(n+7)+·· 4/(1*2*3)+7/(2*3*4)+.+(3n+1)/[n(n+1)(n+2)] 1除以（n+3）(n+4)+1除以(n+4)(n+5)+、、、1除以(n+10)(n+11)=? 证明：1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+) 1+4-7+10-……+(-1)^n(3n+2) 求前N项和 M=(N-1)×1+(N-2)×2+(N-3)×4+(N-4)×8+(N-5)×16+(N-6)×32+(N-7)×64 若n为正整数,求1/n(n+1)+1/(n+1)(n+2)＋1/(n+2)(n+3)+1/(n+3)(n+4)+.+1/