3乘括号1X2加2乘3加3乘4加.九十九乘一百等于 A97X98X99 B98X99X100 C99X100X101 D100X_数学解答

3乘括号1X2加2乘3加3乘4加.九十九乘一百等于 A97X98X99 B98X99X100 C99X100X101 D100X101X102

人气：485 ℃　时间：2020-04-29 07:59:48

解答

1x2 + 2x3 + 3x4 +...+ 99x100=2x2-2 +3x3-3 + 4x4-4 +...+ 100x100-100=2²+3²+4²+...+100² -2-3-4-...-100=1+2²+3²+4²+...+100² -1-2-3-4-...-100=[100*(100+1)(2*100+1)]...