1 2
I , 2,3 , 4,6 ,
9=0,112,3 , 4 6=0
, I
A,B
x
n!
. -
M I
Y I - ' '
c i G DO
as a single D ,
- - - n
1) 4 or 5 or 6 a 7 or 8
2) complementary counting " Total - (O or I or 2 or 3)
k 8 − k
ways(at least 4 b) = ways(4 b) + ways(5 b) + ways(6 b) + ways(7 b) + ways(8 b)
= + + + +( 4 8)(
4 9) (
5 8)(
3 9) (
6 8)(
2 9) (
7 8)(
1 9) (
8 8)(
0 9)
' c- suits of had
6 - 10
x + x + x + x + x = 251 2 3 4 5
( 4 29)
Xi 20
( "EY -
- ( " If )
x ,x ,x ,x ,x ≥ 0 x > 0 x ≥ 1
x = x − 1 x ≥ 0
x + x + x + x + x = 25
x + x + x + x + x = 25 − 5 = 20
x = n
i ′
1 ′
2 ′
3 ′
4 ′
5 ′
- - -
( T) 2 :3 . (2)
htt ) ← * s