(2)P(A)=P(A40A4)=P(A4)+P(A42) 2.3+3.2=3 54545 (3)P(4 44)=P()P(4A)P(4 44) 2131 = 54310 ④P(A4)=P44)_P4)-P44) P(A) P(A) 1-0 =0.5 ⅓(3) ( ) ( ) ( ) 1 2 3 1 2 1 3 1 2 P(A A A ) = P A P A A P A A A 10 1 3 3 4 1 5 2 = ⋅ ⋅ = ( ) ( ) ( ) ( ) （2） P A2 = P A1A2 ∪ A1A2 = P A1A2 + P A1A2 5 3 4 2 5 3 4 3 5 2 = ⋅ + ⋅ = (4) ( ) ( ) ( ) ( ) ( ) ( ) 2 2 1 2 2 1 2 1 2 P A P A P A A P A P A A P A A − = = 1 0.5 5 3 10 3 = − =