Question

已知P(AB)=P(—AB),P(A)=p,求P(B)是多少?

Answer 1

P（AB）+P（-AB）+P（A-B）+P（-A-B）=1;

P（AB）=P(-A-B)=x;

P(A)=P(A-B)+P(AB)=p;

P(A-B)=p-x;

P(-AB)=1-2x-（p-x)=1-x-p;

P(B)=P(AB)+P(-AB)=1-p;