1/2*3/4*5/6*.*2n-1/2n

Sn=n(n+2)(n+4)的分项等于1/6[n(n+2)(n+4)(n+5)-(n-1)n(n+2)(n+4)]吗? n+(n+1)+(n+2)+(n+3)+(n+4)=5n+10这道题怎么解 下列几组力中,合力不可能等于0的是 A.3N 4N 6N B.1N 2N 4N C.2N 4N 6N D.5N 5N 1N 1/[n(n+1)]+1/[(n+1)(n+2)]+1/[(n+2)(n+3)]+1/[(n+3)(n+4)]+[(n+4)(n+5)}怎么算谢谢了, [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 1+(n+2)+(2n+3)+(3n+4)+(4n+5)+……((n-1)n+n)的答案 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n 求证：N=(5^2)*(3^2n+1)*(2^n)-(3^n)*(6^n+2) ∑(∞,n=1)(n^2-2n+3)/(n^4+n^2-6) 求limn→无穷(1+2^n+3^n+4^n+5^n)^1/n 若(n+1)(n+2)比(n+3)(n+4)大6,求n的值 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) 如果n是一个大于6的整数,以下哪个一定能被3整除A n(n+1)(n-4)B n(n+2)(n-1)C n(n+3)(n-5)D n(n+4)(n-2)E n(n+5)(n-6) 一道数论的题n 为大于6的整数, 下面哪个选项可以被3整除?A. n(n+1)(n-4)B. n(n+2)(n-1)C. n(n+3)(n-5)D. n(n+4)(n-2)E. n(n+5)(n-6)需要推导过程 谢谢 2^n*3^n*5^(n+1)/30^n