1⼀1*2*3*4+1⼀2*3*4*5+1⼀3*4*5*6+1⼀4*5*6*7+1⼀5*6*7*8+1⼀6*7*8*9+1⼀7*8*9*10=

2024-12-02 05:53:11
推荐回答(3个)
回答(1):

=1/3[1/(1*2*3)-1/(2*3*4)+1/(2*3*4)-1/(3*3*5)+..-1/(7*8*9)+1/(7*8*9)-1/(8*9*10)]
=1/3(120/720-1/720)
=119/2160

回答(2):

1/3(1/1*2*3-1/2*3*4)+1/3(1/2*3*4-1/3*4*5)+.......+1/3(7*8*9-1/8*9*10)
=1/3(1/1*2*3-1/8*9*10)
=1/3(1/6-1/720)
=119/2160
希望能理解 愿学习进步

回答(3):

400*39/70