1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+.+1/18x19+1/19x20 计算方法与结果

题目

1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+.+1/18x19+1/19x20 计算方法与结果

答案

1/1x2= 1-1/2
1/2x3=1/2-1/3
依此类推
原式 = 1-1/2+1/2-1/3+1/3-...+1/19-1/20
=1-1/20
=19/20