Question

数学学霸在哪里！！！！！

Answer 1

（1）P=1-0.5x0.5x0.5=1-0.125=0.875
（2）P=(7/8x1/8x1/8)x3=21/512
(3)P=1-7/8x7/8x7/8=1-343/512=169/512
(4)补种 P
0 343/512
1 147/512
2 21/512
3 1/512
期望E=0x343/512+1X147/512+2x21/512+3x1/512=3/8
采纳我吧，很辛苦的！

Answer 2

p(x=0)=C(3,0)*[(1/8)^0 ] *[(7/8)^3]=1*1*343/512 =343/512
p(x=1)=C(3,1)*[(1/8)^1 ] *[(7/8)^2]=3*(1/8)*(49/64) =147/512
p(x=2)=C(3,2)*[(1/8)^2 ] *[(7/8)^1]=3*(1/64)*(7/8) =21/512
p(x=3)=C(3,3)*[(1/8)^3] *[(7/8)^0]=1*(1/512)*1 =1/512
期望E(x)=0*343/512+1*147/512+2*21/512+3*1/512
=【0+147+42+3】/512
=192/512