组合题: 1 (1) ,5的4次方=625,
( 2), A(5,4)=5X4X3X2=120
2, C(12,3 ) * C(9,4) *C(5,5)=27720
3, C(5,2) * C(4,0) + C(5,0) * C(4,2)=10+6=16.
4, C(1.1) * C(11,5) =462
5, C(10,2)- C(5,2) - C(3,2) -C(2,2) = 31. 或 C(5,1)*C(2,1) +C(3,1)*C(2,1)+ C(5,1)*C(3,1)
=31
6, C(9,3) - C(5,3) =74
7, C(4,1) +C(4,3)=8