liyao3721
花朵
共回答了18个问题采纳率:100% 举报
其中:C(M,N)表示从M中取N个
1、C(5,1)*C(3,2)+C(5,2)*C(3,1)=5*3+10*3=45
2、C(5,1)*[C(4,1)*C(3,2)+C(4,2)*C(3,1)]+C(5,2)*[C(4,1)*C(3,1)+C(4,2)]+C(5,3)*C(4,1)
=5*(4*3+6*3)+10*(4*3+6)+5*4
=5*30+10*18+20
=350
3、C(5,1)*[C(4,1)*C(7,3)+C(4,2)*C(7,2)+C(4,3)*C(7,1)+C(4,4)]+C(5,2)*[C(4,1)*C(7,2)+C(4,2)*C(7,1)+C(4,3)]+C(5,3)*[C(4,1)*C(7,1)+C(4,2)]
=5*(4*35+6*21+4*7+1)+10*(4*21+6*7+4)+10*(4*7+6)
=5*(140+136+28+1)+10*(84+42+4)+10*(28+6)
=1525+1300+340
=3165
4、C(5,1)*C(11,7)+C(5,2)*C(11,6)+C(5,3)*C(11,5)
=5*330+10*462+10*462
=10890
1年前
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