1/1×2+1/2×3+1/3×4+......+1/8×9+1/9×10
来源:百度知道 编辑:UC知道 时间:2024/05/25 03:42:16
1/1×2+1/2×3+1/3×4+......+1/8×9+1/9×10
=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/9-1/10)
中间正负抵消
=1-1/10
=9/10
原式=1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10=1-1/10=0.9
这是一个很常用的列项法。谨记~!!
1/1×2+1/2×3+1/3×4+......+1/8×9+1/9×10
=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/9-1/10)
中间正负抵消
=1-1/10
=9/105
1+1/2+1/3+.......+1/n=?
1+1/2+1/3+1/4...+1/n=?
1/2+1/4+1/8+1/16+……+1/256+1/512
1+1/2+1/3+1/4+1/5+1/6+1/7+1/8+......+1/100 = ?
(1-1/2)+(1/2-1/3)+(1/3-1/4)+..(1/2001-1/2002) 1/1x2+1/2x3+1/3x4+..+1/2001x2002
1×1/2+2×1/3+3×1/4+4×1/5+5×1/6+……98×1/99+99×1/100
1+1/(1+2)+1/(1+2+3)+…+1/(1+2+3+…+n)
1+1/(1+2) 1/(1+2+3)……+1/(1+2+3……+100)
1/2+2/1*2*3+3/1*2*3*4+。。。+n/(n+1)!=?
(1+1/2)(1+1/3+(1+1/4)……(1+1/100)/(1-1/2)(1-1/3)(1-1/4)……(1-1/100)