# 1) A1 A2 be two events, show that P (A1 ∩ A2) ≤ P (A1) . P

1. Jul 27, 2011

### kezman

1) A1 A2 be two events, show that P (A1 ∩ A2) ≤ P (A1) . P (A2)
2) show that P (A1 ∩ A2 ∩ ... ... An) ≤ P (A1) . P (A2) . ... ... ... ... P (An)
4)
show that P (A + B) + P (/ A + / B) = 1

I have problems with these exercises. I dont know if I copied them wrong.
thanks

2. Jul 27, 2011

### LCKurtz

Re: Probabilities

Why don't you look and see if you copied them wrong?

What if A1 = A2 and P(A1) = 1/2?

And what does A+B mean for sets A and B? And what does /A mean?

3. Jul 27, 2011

### kezman

Re: Probabilities

I dont have the original statements, but we were looking for a counterexample. The last one instead of plus is union and / is complement. Im sure that one is false too.

4. Jul 27, 2011

### LCKurtz

Re: Probabilities

Me too.

5. Jul 28, 2011

### uart

Re: Probabilities

So that means you are trying to disprove them. It would have been useful if you had of stated that at the outset.

6. Jul 28, 2011

### Staff: Mentor

Re: Probabilities

Are Venn diagrams good enough for demonstrating this?

7. Jul 28, 2011

### kezman

Re: Probabilities

thanks everybody for the help. At the beggining we didnt know if there were ok or not. Now we are sure. thanks