Let E1 and E2 be two independent events such that P(E1)=P1 and P(E2)=P2. Describe in words of the events whose probabilities are
P1+P2−2P1P2
P(E1)=P1 and P(E2)=P2
P1+P2−2P1P2=P(E1)+P(E2)−2P(E1).P(E2)=P(E1)+P(E2)−2P(E1∩E2)=P(E1∪E2)−P(E1∩E2)
So, either E1 or E2 occurs but not both.