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

2024-12-05 06:01:16
推荐回答(1个)
回答1:

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