三个条件概率公式的推导

p(a+b+c)=p(a+b)+p(c)-p[(a+b)c]
=p(a)+p(b)-p(ab)+p(c)-p(ac+bc)
=p(a)+p(b)-p(ab)+p(c)-[p(ac)+p(bc)-p(acbc)]
=p(a)+p(b)-p(ab)+p(c)-[p(ac)+p(bc)-p(abc)]
=p(a)+p(b)-p(ab)+p(c)-p(ac)-p(bc)+p(abc)
=p(a)+p(b)+p(c)-p(ab)-p(ac)-p(bc)+p(abc)