$直線排列$
$ 將A,B,C,D\;四個字母中，\;任取\;3\;個排成一列，\;試寫出所有方法數 $

$Step=%v$

$ Angel $

$ Barbie $

$ Cherry $

$ Debby $

$(1) \;總共有幾種排列方法？$
$(2)\;A,B,C,D各出現幾次？$
$(3)\;A,B,C,D在三個位置各出現幾次？$

A = (-3.88, -1.06)
B: A + (4, 0)
C: A + (8, 0)
s = 0 (slider from 0 to 25, step 1)
text2: "$ " + (LaTeX[If[s ≥ 1, "ABC"]]) + "\; \;\;\;" + (LaTeX[If[s ≥ 13, "CAB"]]) + "$
$" + (LaTeX[If[s ≥ 2, "ABD"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 14, "CAD"]]) + "$
$" + (LaTeX[If[s ≥ 3, "ACB"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 15, "CBA"]]) + "$
$" + (LaTeX[If[s ≥ 4, "ACD"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 16, "CBD"]]) + "$
$" + (LaTeX[If[s ≥ 5, "ADB"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 17, "CDA"]]) + "$
$" + (LaTeX[If[s ≥ 6, "ADC"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 18, "CDB"]]) + "$
$" + (LaTeX[If[s ≥ 7, "BAC"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 19, "DAB"]]) + "$
$" + (LaTeX[If[s ≥ 8, "BAD"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 20, "DAC"]]) + "$
$" + (LaTeX[If[s ≥ 9, "BCA"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 21, "DBA"]]) + "$
$" + (LaTeX[If[s ≥ 10, "BCD"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 22, "DBC"]]) + "$
$" + (LaTeX[If[s ≥ 11, "BDA"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 23, "DCA"]]) + "$
$" + (LaTeX[If[s ≥ 12, "BDC"]]) + "\;\;\;\;" + (LaTeX[If[s ≥ 24, "DCB"]]) + "$"