奥数1/2x1/3x1/4+1/3x1/4x1/5+……+1/8x1/9x1/10

奥数1/2x1/3x1/4+1/3x1/4x1/5+……+1/8x1/9x1/10
奥数1/2x1/3x1/4+1/3x1/4x1/5+……+1/8x1/9x1/10

奥数1/2x1/3x1/4+1/3x1/4x1/5+……+1/8x1/9x1/10
1/2(1/2x3-1/3x4)+1/2(1/3x4-1/4x5)+……+1/2(1/8x9-1/9x10)=
1/2(1/2x3-1/9x10)=
1/2x14/90=
7/90
我对象做的,

打酱油

。