1⼀(1x2x3)+1⼀(2x3x4)+1⼀(3x4x5)+........1⼀(10X11X12)

2024-12-15 16:07:40
推荐回答(1个)
回答1:

=1/2(1/1×2-1/2×3+1/2×3-1/3×4+……+1/10×11-1/11×12)
=1/2(1/1×2-1/11×12)

=65/264