数学符号c上4下8怎么算？ 概率问题C上4下8分子等于8×7×6×5，分母等于4×3×2...
\u6570\u5b66\u7b26\u53f7c\u4e0a4\u4e0b8\u600e\u4e48\u7b97\uff1f\u8fd9\u662f\u6c42\u7ec4\u5408\u95ee\u9898\uff1a
8\u00d77\u00d76\u00d75\u00f7\uff081\u00d72\u00d73\u00d74\uff09
=1680\u00f724
=70
\u6570\u5b66\u4e2dC\u4e0a\u6807\u548c\u4e0b\u6807\u7684\u516c\u5f0f\u4ee3\u8868\u7ec4\u5408\u6570\u3002\u516c\u5f0f\u5982\u4e0b\uff1a
\u6392\u5217\u7ec4\u5408\u8ba1\u7b97\u65b9\u6cd5\u5982\u4e0b\uff1a
\u6392\u5217A(n\uff0cm)=n\u00d7\uff08n-1\uff09\u3002\uff08n-m+1\uff09=n!/\uff08n-m\uff09!(n\u4e3a\u4e0b\u6807\uff0cm\u4e3a\u4e0a\u6807\uff0c\u4ee5\u4e0b\u540c)
\u7ec4\u5408C(n\uff0cm)=P(n\uff0cm)/P(m\uff0cm) =n!/m!\uff08n-m\uff09!\uff1b
\u4f8b\u5982\uff1a
A(4\uff0c2)=4!/2!=4*3=12
C(4\uff0c2)=4!/(2!*2!)=4*3/(2*1)=6
C8(4)=A8(4)/A4(4)=(8*7*6*5)/(4*3*2*1)
\u4e4b\u6240\u4ee5\u5206\u5b50\u4ed6\u4e0d\u62104 3 2 1\uff0c\u662f\u56e0\u4e3a\u5206\u5b50\u53ea\u67094\u9879\uff0c\u5c31\u60f3\u6709\u516b\u672c\u4e66\uff0c\u9009\u56db\u672c\u51fa\u6765\uff0c\u53ea\u80fd\u90094\u4e0b\uff0c8*7*6*5\uff0c\u7136\u540e\u7ec4\u5408\u5728\u4e00\u8d77\uff0c\u80af\u5b9a\u662f\u8981\u9664\u4ee54*3*2*1
\u6269\u5c55\u8d44\u6599
\u6982\u7387\u7684\u8ba1\u7b97\uff0c\u662f\u6839\u636e\u5b9e\u9645\u7684\u6761\u4ef6\u6765\u51b3\u5b9a\u7684\uff0c\u6ca1\u6709\u4e00\u4e2a\u7edf\u4e00\u7684\u4e07\u80fd\u516c\u5f0f\u3002\u89e3\u51b3\u6982\u7387\u95ee\u9898\u7684\u5173\u952e\uff0c\u5728\u4e8e\u5bf9\u5177\u4f53\u95ee\u9898\u7684\u5206\u6790\u3002\u7136\u540e\uff0c\u518d\u8003\u8651\u4f7f\u7528\u9002\u5b9c\u7684\u516c\u5f0f\u3002
\u4f46\u662f\u6709\u4e00\u4e2a\u516c\u5f0f\u662f\u5e38\u7528\u5230\u7684\uff1a
P(A)=m/n
\u201c(A)\u201d\u8868\u793a\u4e8b\u4ef6
\u201cm\u201d\u8868\u793a\u4e8b\u4ef6\uff08A\uff09\u53d1\u751f\u7684\u603b\u6570
\u201cn\u201d\u662f\u603b\u4e8b\u4ef6\u53d1\u751f\u7684\u603b\u6570
=1/2*7*5
=1/70
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绛旓細濡侰8涓婇潰鏄2锛屽氨鏄(8*7)/(2!)=28
