已知:12+22+32+…+n^2=16n(n+1)(2n+1),试求22+42+62+…+1002

已知:12+22+32+…+n^2=16n(n+1)(2n+1),试求22+42+62+…+1002 已知:12+22+32+…+n2=1/6n(n+1)(2n+1),试求22+42+62+…+1002 已知12+22+32+….n2=(1/6)n(n+1)(2n+1),试求22+42+62….+502的值(写过程) 已知Sn=2+5n+8n^2+…+(3n-1)n^n-1(n∈N*)求Sn 12+22+32+42+……+n2=n+(n+1)(2n+1)/6为什么? 求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n), 求极限 lim n[1/(n^2+1)+1/(n^2+2^2）+……+1/(n^n+n^n)] (n趋向于无穷大,n^n 已知a(n)=1/(n+1)*(n+1),f(n)=[1-a(1)]*…*[1-a(n)],试求f(1),f(2),f( 证明：12+22+32+……+n2=1/6n(n+1)(2n+1) 12+22+32+42+52+62+72+82+…+n2=n(n+1)(2n+1)/6 已知1/n^2+3n=A/n+B/n+3,求ab? f(n)=1/(n+1) + 1/(n+2) + 1/(n+3) + …… + 1/(2n),(n∈整数,且n≥2),求