1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 04:34:06
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11

1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11

1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11
=10×(10+1)×(10+2)÷3
=10×11×12÷3
=110×12÷3
=1320÷3
=440

n=10 ,很好算得,得440。也许我的方法很麻烦,但是思路是很不错的,可以1x2 2x3 3x4 4x5 5x6 6x7 7x8 8x9 9x10 10x11 =2 6 12 20