一圆形靶分成A,B,C三个部分面积比为1:1:2某同学向该靶投掷三枚飞镖每次一枚假设他每次投掷必中靶且随机投掷 1该同学在一次投掷中投入A区域的概率 2 设X表示该同学在3次投掷投中A区雨的次数 求X的分布列及期望

1.P=1/4
2.P(X=0)=C(3,0)*(3/4)^3=27/64
P(X=1)=C(3,1)*(1/4)*(3/4)^2=27/64
P(X=2)=C(3,2)*(1/4)^2*(3/4)=9/64
P(X=3)=C(3,3)*(1/4)^3=1/64
E(X)=0*27/64+1*27/64+2*9/64+3*1/64=3/4

1.P=1/4
2.P(X=0)=C(3,0)*(3/4)^3=27/64
P(X=1)=C(3,1)*(1/4)*(3/4)^2=27/64
P(X=2)=C(3,2)*(1/4)^2*(3/4)=9/64
P(X=3)=C(3,3)*(1/4)^3=1/64
E(X)=0*27/64+1*27/64+2*9/64+1*1/64=23/32