如题所述
第1个回答 2014-03-28
求和吧？
n(n+1)=n²+n
原式=(1²+1)+(2²+2)+(3²+3)+...+(100²+100)
=(1²+2²+3²+...+100²)+(1+2+3+...+100)
=100*101*201/6+5050
=343400
n(n+1)=n²+n
原式=(1²+1)+(2²+2)+(3²+3)+...+(100²+100)
=(1²+2²+3²+...+100²)+(1+2+3+...+100)
=100*101*201/6+5050
=343400
第2个回答 2014-03-28
1x2+2x3+3x4+.....+100x101
=1/3x1x2x3+1/3[2x3x4-1x2x3]+1/3[3x4x5-2x3x4]+....+1/3[100x101x102-99x100x101]
=1/3[1x2x3+2x3x4-1x2x3+3x4x5-2x3x4+...+100x101x102-99x100x101]
=1/3x100x101x102
=343400本回答被网友采纳
=1/3x1x2x3+1/3[2x3x4-1x2x3]+1/3[3x4x5-2x3x4]+....+1/3[100x101x102-99x100x101]
=1/3[1x2x3+2x3x4-1x2x3+3x4x5-2x3x4+...+100x101x102-99x100x101]
=1/3x100x101x102
=343400本回答被网友采纳
