請問第五題如何做?
5. 由1,2,3,.....,20挑出\(\displaystyle x_{1}, x_{2}, x_{3}\)三個數字, 且\(\displaystyle x_{1}\) <\(\displaystyle x_{2}\)<\(\displaystyle x_{3}\)
,求\(\displaystyle x_{1}與 x_{2}\)至少差3, \(\displaystyle x_{2}與 x_{3}\)至少差5的機率?
[ 本帖最後由 zero 於 2011-9-12 03:39 PM 編輯 ]
