# Thread: Showing that X1+X2=2X1 for random variable X1, X2 such that X1=X2

1. ## Showing that X1+X2=2X1 for random variable X1, X2 such that X1=X2

I need help understanding this problem.

Say that X1=X2 which means that the random variable X1 and X2 are equal in distribution. This means that these two random variables have the same distribution, same mean and same variance. These two random variables are independent. Is it true that X1+X2=2X1?

In my head this makes perfect sense but i am having trouble writing a proof to this.

2. Originally Posted by ajorge
I need help understanding this problem.

Say that X1=X2 which means that the random variable X1 and X2 are equal in distribution. This means that these two random variables have the same distribution, same mean and same variance. These two random variables are independent. Is it true that X1+X2=2X1?

In my head this makes perfect sense but i am having trouble writing a proof to this.
Just Mean and Variance?

Do you mean IDENTICAL, or just the first two moments?

3. Originally Posted by tkhunny
Just Mean and Variance?

Do you mean IDENTICAL, or just the first two moments?
From my understanding the question only has those two moments and they are identical.

4. From my understanding those are two moments that are Identical

5. Originally Posted by ajorge
From my understanding those are two moments that are Identical

Can you write out the definition of E[X1]? That should get you started.

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